Two-wire communication protocol engine

CROSS-REFERENCE TO RELATED APPLICATIONS

0001This application claims the benefit of priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 61/843,891, entitled “A2B Protocol Engine” filed Jul. 8, 2013, U.S. Provisional Application Ser. No. 61/843,896, entitled “Digital Phase Detector” filed Jul. 8, 2013, U.S. Provisional Application Ser. No. 61/843,902, entitled “Differential Decoder” filed Jul. 8, 2013, U.S. Provisional Application Ser. No. 61/845,542, entitled “System and Method for Implementing A2B Protocol” filed Jul. 12, 2013, which are hereby incorporated by reference in their entireties. This application is also a continuation-in-part and claims the benefit of priority under 35 U.S.C. §120 of U.S. application Ser. No. 13/646,397, filed Oct. 5, 2012, entitled “Two-Wire Communication System for High Speed Data and Power Distribution” and U.S. application Ser. No. 13/646,382, filed Oct. 5, 2012, entitled “Methods for Discovery, Configuration, and Coordinating Data Communications Between Masters and Slave Devices in a Communication System.” The disclosures of the prior Applications are considered part of and are incorporated by reference in the disclosure of this Application.

TECHNICAL FIELD OF THE DISCLOSURE

0002The present disclosure relates generally to communication bus technology and, more particularly, to a two-wire communication protocol engine.

BACKGROUND

0003Two-wire conductor systems are known in electrical and electronics fields as a means of data and power transmission. Such systems typically employ a controller that drives power into two wire conductors, controls the timing of data transfer and transmits and receives data. A master device (also called a master node) is controlled by the controller, and the master node in turn controls one or more slave devices (also called slave nodes). Generally, communication on the two-wire conductor system involves sending a clock signal on one wire and data signal on the other wire, with the rise and/or fall of the clock signal indicating data transfer between the connected devices. Two-wire conductor systems can be used in myriad applications, such as control systems in automobiles, audio signal processing, telephony, etc.

Overview

0004The present disclosure relates generally to a two-wire communication protocol engine. Specifically, proliferation of sensors, such as microphones, cameras, etc. in automobiles (and other such closed and/or mobile systems that utilize sensors and other peripheral devices) can lead to excessive amount of wiring, with consequent increase in system complexity and weight, and potential decrease in performance and reliability. A particular type of two-wire communication, called automobile audio bus (A²B) communication, can be used in automobiles and other similar systems to reduce complexity of data and power transmission across the various sensors and sensor control devices. The A²B bus provides a multi-channel, Inter-Integrated Circuit sound (I²S)/time division multiplexed (TDM) link between connected nodes. It embeds bi-directional synchronous data (e.g., digital audio), clock and synchronization signals onto a single differential wire pair. A²B supports a direct point-to-point connection and allows multiple, daisy chained nodes at different locations to contribute or consume TDM channel content. The A²B bus allows time for downstream traffic (e.g., from the master node to the last slave node) and upstream traffic (e.g., to the master node) and allows power transmission over the same twisted wire pair.

0005In an example embodiment, a two-wire communication (A²B) protocol engine manages control and data transmissions in a bi-directional, multi-node bus system where each node is connected over a twisted wire pair bus to another node. Some embodiments include a state machine that allows for synchronized updates of configuration data across the system, a distributed interrupt system, a synchronization pattern based on data coding used in the system, and data scrambling applied to a portion of the data transmitted over the twisted wire pair bus. The multi-node bus system comprises a master node and a plurality of slave nodes. The slave nodes can be powered over the twisted wire pair bus.

BRIEF DESCRIPTION OF THE DRAWINGS

0006<figref idref="DRAWINGS">FIG. 1</figref> is a simplified block diagram illustrating a schematic of an illustrative system including a two-wire communication protocol engine;

0007<figref idref="DRAWINGS">FIG. 2</figref> is a simplified block diagram illustrating example details of an embodiment of the system;

0008<figref idref="DRAWINGS">FIG. 3</figref> is a simplified block diagram illustrating other example details of an embodiment of the system;

0009<figref idref="DRAWINGS">FIG. 4</figref> is a simplified block diagram illustrating yet other example details of an embodiment of the system;

0010<figref idref="DRAWINGS">FIG. 5</figref> is a simplified diagram illustrating yet other example details of an embodiment of the system;

0011<figref idref="DRAWINGS">FIG. 6</figref> is a simplified diagram illustrating yet other example details of an embodiment of the system;

0012<figref idref="DRAWINGS">FIG. 7</figref> is a simplified block diagram illustrating yet other example details of an embodiment of the system;

0013<figref idref="DRAWINGS">FIG. 8</figref> is a simplified logic diagram illustrating yet other example details of an embodiment of the system;

0014<figref idref="DRAWINGS">FIG. 9</figref> is a simplified graph illustrating yet other example details of an embodiment of the system;

0015<figref idref="DRAWINGS">FIG. 10</figref> is a simplified diagram illustrating yet other example details of an embodiment of the system;

0016<figref idref="DRAWINGS">FIG. 11</figref> is a simplified diagram illustrating yet other example details of an embodiment of the system;

0017<figref idref="DRAWINGS">FIG. 12</figref> is a simplified flow diagram illustrating example operations that may be associated with an embodiment of the system;

0018<figref idref="DRAWINGS">FIG. 13</figref> is a simplified flow diagram illustrating other example operations that may be associated with an embodiment of the system; and

0019<figref idref="DRAWINGS">FIG. 14</figref> is a simplified flow diagram illustrating yet other example operations that may be associated with an embodiment of the system.

DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE DISCLOSURE

0020<figref idref="DRAWINGS">FIG. 1</figref> is a simplified block diagram illustrating a system <b>10</b> including a two-wire communication protocol engine. System <b>10</b> comprises a plurality of nodes <b>12</b>(<b>1</b>)-<b>12</b>(N). <b>12</b>(<b>1</b>) represents a master node, which communicates with three slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N) over a twisted wire pair bus <b>14</b> using a two-wire communication protocol (e.g., A²B protocol). Each slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) may read and/or write data from/to one or more sensors or other peripheral devices <b>16</b>. Examples of peripheral devices include microphones (mics), mic arrays, digital to analog converters (DACs), etc. A host controller <b>18</b> may communicate with and control master node <b>12</b>(<b>1</b>) over multi-channel I²S and Inter-Integrated Circuit (I²C) communication protocols. Embodiments of the A²B protocol engine may allow for control information and audio data to be transmitted in both directions using twisted wire pair bus <b>14</b> to connect each node to the next one. Slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N) can also be powered by twisted wire pair <b>14</b>.

0021As used herein, the term “node” refers to an integrated circuit, device or other such object capable of sending and receiving data (e.g., electrical signals) over appropriate communications channels in an electrical circuit. The “master node” comprises an originator of a clock signal (e.g., which can be derived from an I²S input), downstream data, network control and power; the master node is programmed by host controller <b>18</b> (e.g., microprocessor), and it receives/sends payload to/from host controller <b>18</b>. The “slave node” comprises an addressable network connection point that can represent a possible destination for downstream data frames (e.g., single block of payload of a specific node with possibly multiple synchronous data slots of content) and source of upstream data frames. Synchronous data refers to continuously streamed data (e.g., audio signal) in which a fixed time interval (e.g., 48 kHz) and a fixed phase spaces two corresponding transitions.

0022In various embodiments, each node <b>12</b>(<b>1</b>)-<b>12</b>(N) may include an A²B protocol engine implemented, for example, in a portion of an integrated circuit. In various embodiments, the A²B protocol engine manages control and data transmissions in the linear, bi-directional, multi-node bus system. According to various embodiments, the integrated circuit comprising the A²B protocol engine can work well in a noisy environment, for example, by minimizing electromagnetic emissions. Each protocol engine may include a state machine that allows for synchronized updates of programmed data across system <b>10</b>, a distributed interrupt system, a synchronization pattern based on data coding used in the two-wire communication protocol, and data scrambling applied to a portion of the data traversing twisted wire pair bus <b>14</b>. Another feature includes a simplified floating-point compression to compress data before it is transmitted across twisted wire pair bus <b>14</b>.

0023In a general sense, the A²B protocol can connect multi-channel I²S synchronous, pulse code modulated (PCM) data between nodes <b>12</b>(<b>1</b>)-<b>12</b>(N). The A²B protocol can also extend the synchronous, time division multiplexed (TDM) nature of I²S to system <b>10</b> that connects multiple nodes <b>12</b>(<b>1</b>)-<b>12</b>(N), where each node <b>12</b>(<b>1</b>)-<b>12</b>(N) can consume data, provide data, or both.

0024According to various embodiments, master node <b>12</b>(<b>1</b>) may be configured (e.g., programmed, designed, etc.) through an integrated I²C port. Master node <b>12</b>(<b>1</b>) may generate downstream A²B transactions (e.g., data signals, power signals, etc.) and receive upstream A²B transactions. Data received via twisted wire pair <b>14</b> may be written into an A²B frame buffer and transmitted out of master node <b>12</b>(<b>1</b>) through two I²S transmitters. Data to be transmitted via A²B may be read from the A²B frame buffer, which may be filled by two I²S receivers. In some embodiments, master node <b>12</b>(<b>1</b>) comprises state machines to manage the A²B protocol including discovery (e.g., of slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N)), broadcast writes (e.g., of system wide information, configuration changes, etc.), CRC generation of synchronization control frames, cyclic redundancy check (CRC) error detection and handling for synchronization response frames, CRC error detection and handling for interrupt frames, parity generation for downstream data, and parity checks and error handling for upstream data (among other features).

0025Each slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) may be configured through the upstream A²B port. Each slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) may receive downstream A²B transactions and optionally retransmit the transactions further downstream. Each slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) may either receive or generate upstream A²B transactions, optionally retransmit data upstream, and optionally add data to the upstream transaction. Data received via A²B may be written into the A²B frame buffer and transmitted out through two I²S transmitters. Data to be transmitted via A²B may be read from the A²B frame buffer, which may be filled by two I²S receivers and/or by a PDM interface. Each slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) may comprise corresponding state machines to manage A²B protocol, similar to the state machine on master node <b>12</b>(<b>2</b>). The I²C Interface of each slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) may be used as a master to control attached nodes. Commands may be sent from host controller <b>18</b> over twisted wire pair bus <b>14</b> and passed to a slave node through the I²C Interface. The A²B protocol can comprise a single-master, multiple-slave system where master node <b>12</b>(<b>1</b>) is controlled by host controller <b>18</b>. Host controller <b>18</b> can generate a periodic synchronization signal on its I²S TDM interface at a fixed frequency (e.g., 48 kHz) to which all A²B nodes <b>12</b>(<b>1</b>)-<b>12</b>(N) may synchronize.

0026During operation, when system <b>10</b> is communicating data between various nodes <b>12</b>(<b>2</b>)-<b>12</b>(N), each node may be configured to handle data on twisted wire pair bus <b>14</b>. Communications along A²B twisted wire pair bus <b>14</b> occurs in periodic superframes. Each superframe is divided into periods of downstream transmission (also called downstream portions), upstream transmission (also called upstream portions), and no transmission (where the bus is not driven). For example, master node <b>12</b>(<b>1</b>) may be programmed with a number of downstream portions to transmit to slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N), and a number of upstream portions to receive from slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N). Slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N) may be programmed with a number of downstream portions to retransmit down A²B twisted wire pair bus <b>14</b>, a number of downstream portions to consume, a number of upstream portions to retransmit up A²B twisted wire pair bus <b>14</b>, and a number of upstream portions to transmit received data from corresponding peripheral devices <b>16</b>.

0027It may be noted that although only four nodes <b>12</b>(<b>1</b>)-<b>12</b>(N) are shown herein for sake of simplicity, any number of nodes may be interconnected in a similar manner within the broad scope of the embodiments of system <b>10</b>. Moreover, each slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) may communicate with any number of peripheral devices within the broad scope of the embodiments.

0028Turning to <figref idref="DRAWINGS">FIG. 2</figref>, <figref idref="DRAWINGS">FIG. 2</figref> is a simplified block diagram illustrating an example node <b>12</b> according to an embodiment of system <b>10</b>. Node <b>12</b> can include two Low Voltage Differential Signaling (LVDS) transceivers (XCVRs), namely, LVDS XCVR <b>26</b> and LVDS XCVR <b>28</b>. Each LVDS transceiver <b>26</b> and <b>28</b> has a positive pad (P) and a negative pad (N). The positive pad (e.g., AP) of one transceiver on one node connects to another positive pad (e.g., BP) on another transceiver on another node. Likewise, the negative pad (e.g., AN) of one transceiver on one node connects to another negative pad (e.g., BN) on another transceiver on another node. An A2B digital logic module <b>30</b> may communicate (e.g., through electronic signals) with a phased locked loop (PLL) <b>32</b>, a low dropout regulator (LDO) <b>34</b> and a line power switch <b>36</b> (among other components). Various digital pads (e.g., pins) <b>38</b> may carry signals in and out of node <b>12</b>.

0029Turning to <figref idref="DRAWINGS">FIG. 3</figref>, <figref idref="DRAWINGS">FIG. 3</figref> is a simplified block diagram illustrating an example A²B digital logic module <b>30</b> according to an embodiment of system <b>10</b>. A²B digital logic module <b>30</b> may include an A²B protocol engine <b>40</b>, an A²B frame buffer <b>42</b>, and an A²B data encoding and recovery module <b>44</b> (among other components). Digital pads <b>38</b> may provide pins for various input/output functionalities. For example, node <b>12</b> may operate as an A²B master node when a MSTR pin <b>46</b> is held high and as a A²B slave node when MSTR pin <b>46</b> is held low. When node <b>12</b> is pin-programmed as a master node, then it may be a slave node to its I²S and I²C ports. If node <b>12</b> is pin-programmed as an A²B slave node, then it may function as the master node of its I²S and I²C ports.

0030A DOUT/DIN pin <b>48</b> may allow node <b>12</b> to create event driven interrupt requests towards host controller <b>18</b>. DOUT/DIN pin <b>48</b> can serve as a general-purpose input/output (IO) pin in a slave node mode (e.g., when MSTR pin is set to low), with interrupt request input capability. A DIN/DOUT <b>50</b> pin can server as a digital input in a master mode (e.g., when MSTR pin <b>46</b> is set to high) and as a digital output in slave node (e.g., when MSTR pin <b>46</b> is set to low).

0031Turning to <figref idref="DRAWINGS">FIG. 4</figref>, <figref idref="DRAWINGS">FIG. 4</figref> is a simplified block diagram illustrating example details of an A²B protocol engine <b>40</b> according to an embodiment of system <b>10</b>. A²B protocol engine <b>40</b> may include an I²C Interface <b>52</b> that provides an I²C slave on a master node to allow programming access to host controller <b>18</b>. I²C interface <b>52</b> may also provide an I²C master on a slave node to allow programming over distance from host controller <b>18</b>. A²B protocol engine <b>40</b> may include a control module <b>54</b> that can control the A²B protocol, generate synchronization frames for transmission (TX), generates interrupt request (IRQ) frames for upstream TX, receive synchronization frames for reception (RX). Control module <b>54</b> may include programmable registers.

0032A preamble logic module <b>56</b> can generate a preamble for synchronization frames for TX, and receive preamble from synchronization frames from RX. In specific embodiments, a downstream control frame preamble is sent by master node <b>12</b>(<b>1</b>) every 1024 bits. Slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N) may synchronize to the downstream control preamble and generate their local, phase aligned master clock from the preamble. A CRC insert module <b>58</b> can generate CRC for synchronization frames for TX. A frame/compress module <b>60</b> can take data from A²B frame buffer <b>42</b>, optionally compress data, and optionally generate parity for data. A Multiplexer (Mux) <b>62</b> may multiplex the preamble from preamble logic <b>56</b>, synchronization frames, IRQ frames, and data into a TX stream. The TX stream may be scrambled by a scramble module <b>64</b>.

0033The RX stream entering node <b>12</b> may be descrambled by a descramble module <b>66</b>. A demultiplexer (Demux) <b>68</b> may demultiplex preamble, synchronization frames, IRQ frames, and data from the RX stream. Another CRC Check module <b>58</b> on the RX side may check received synchronization frames for correct CRC. A deframe/decompress module <b>70</b> may accept RX data, optionally check parity, optionally decompress data, and write the RX data to A²B frame buffer <b>42</b>. An LFSR module <b>72</b> may generate a pseudo-random bit stream to be used in system evaluation.

0034Turning to <figref idref="DRAWINGS">FIG. 5</figref>, <figref idref="DRAWINGS">FIG. 5</figref> is a simplified block diagram illustrating an example synchronization pattern <b>80</b> according to an embodiment of system <b>10</b>. Because twisted wire bus <b>14</b> provides transmission in both directions, the A²B protocol is broken up into a downstream portion, wherein a control frame and downstream data are transmitted from the master node (e.g., <b>12</b>(<b>1</b>)); and an upstream portion, wherein a response frame and upstream data are transmitted to the master node (e.g., <b>12</b>(<b>1</b>)) from each of the slave nodes (e.g., <b>12</b>(<b>2</b>)-<b>12</b>(N)). Each slave node (e.g., <b>12</b>(<b>2</b>)-<b>12</b>(N)) can use a beginning portion of the received control frame as a time base feeding a PLL. Hence, the control frame may begin with a synchronization pattern that is not replicated by the data patterns.

0035According to various embodiments, clock first, transition on zero Differential Manchester Coding can used in the A2B protocol. According to the encoding scheme, each bit time begins with a clock transition. If the data value is zero, the encoded signal transitions again in the middle of the bit time. If the data value is one, the encoded signal does not transition again. Synchronization pattern <b>80</b> includes a preamble pattern <b>82</b> and a data pattern <b>84</b>.

0036Preamble pattern <b>82</b> may violate the encoding protocol (e.g., clock transitions do not occur at the beginning of bit times <b>5</b>, <b>7</b>, and <b>8</b>), which means that preamble pattern <b>82</b> may not match any legal (e.g., appropriate, correctly encoded) data pattern <b>84</b>. In addition, preamble pattern <b>82</b> cannot be reproduced by taking a legal data pattern <b>84</b> and forcing twisted wire pair <b>14</b> high or low for a single bit time or for a multiple bit time period. In various embodiments, different preamble patterns that violate the encoding used for data pattern <b>84</b> may be implemented in synchronization pattern <b>80</b>. The example preamble illustrated herein has pulse widths not longer than one bit clock, and is merely provided as an example, and not as a limitation of embodiments of system <b>10</b>.

0037The A²B digital logic module can include a Differential Manchester decoder block that runs on a clock recovered from twisted wire pair bus <b>14</b> and that detects synchronization pattern <b>80</b> to send a frame sync pulse to the PLL. Hence, synchronization pattern <b>80</b> can be detected without using a system clock or a higher speed oversampling clock. Thus, the slave nodes (e.g., <b>12</b>(<b>2</b>)-<b>12</b>(N)) can receive a PLL synchronization signal from twisted wire pair bus <b>14</b> without requiring a crystal clock source at the slave nodes (e.g., <b>12</b>(<b>2</b>)-<b>12</b>(N)).

0038Turning to <figref idref="DRAWINGS">FIG. 6</figref>, <figref idref="DRAWINGS">FIG. 6</figref> is a simplified diagram of a superframe <b>90</b> used in the A²B protocol according to an embodiment of system <b>10</b>. Communications along A²B twisted wire pair bus <b>14</b> can occur in periodic superframes. A superframe frequency may be same as a synchronization signal frequency. Data may be transferred at a bit rate that is 1024 time faster (e.g., 49.152 MHz). Each superframe <b>90</b> may be divided into periods of downstream transmission <b>92</b>, upstream transmission <b>94</b>, and no transmission <b>96</b> (e.g., wherein A²B twisted wire pair bus <b>14</b> is not driven).

0039Example superframe <b>90</b> is shown with an initial period of downstream transmission <b>92</b> and a later period of upstream transmission <b>94</b>. Substantially all signals on A²B twisted wire bus <b>14</b> may be line coded and the synchronization signal forwarded downstream from the master node (e.g., <b>12</b>(<b>1</b>)) to the last slave node (e.g., <b>12</b>(N)) in a form of synchronization preamble pattern <b>82</b>. Preamble pattern <b>82</b> may be followed by control data pattern <b>84</b> to build a synchronization control frame. Downstream, TDM synchronous data may be added directly after the control frame.

0040Each slave node (e.g., <b>12</b>(<b>2</b>)-<b>12</b>(N)) may consume a portion of the downstream data. The last slave node (e.g., <b>12</b>(N)) may respond after the response time with a response frame. Upstream synchronous data may be added by each slave node directly after the response frame. Substantially all synchronous data may be organized into data slots of equal width. A data slot refers to synchronous data signal of a single peripheral device <b>14</b> (e.g., microphone or speaker) as mapped onto twisted wire pair bus <b>14</b>. Other slave nodes (e.g., <b>12</b>(<b>2</b>)-<b>12</b>(<b>3</b>)), which are not the last slave node (e.g., <b>12</b>(N)) may replace the response frame if a read of a register is requested in the control frame or if a remote I²C read is requested in the control frame. The embedded control frame and response frame can allow host controller <b>18</b> to individually address each slave node (e.g., <b>12</b>(<b>2</b>)-<b>12</b>(N)).

0041Turning to <figref idref="DRAWINGS">FIG. 7</figref>, <figref idref="DRAWINGS">FIG. 7</figref> is a simplified diagram illustrating an example state machine <b>100</b> at master node <b>12</b>(<b>1</b>) according to an embodiment of system <b>10</b>. Each node <b>12</b>(<b>1</b>)-<b>12</b>(N) may accept changes to its configuration (e.g., number of downstream and upstream portions of superframes to transmit, receive and consumer) simultaneously. Because system <b>10</b> is distributed and control and response frames may be corrupted by noise, the A²B protocol engine may include a state machine, for example, to synchronize the time at which changes to the configuration are accepted.

0042An example version of state machine <b>100</b> according to the A²B protocol starts with an initial state <b>102</b> of STATE<b>0</b>. When master node <b>12</b>(<b>1</b>) is in the initial state <b>102</b> STATE<b>0</b>, it may receive a NEW STRUCTURE command (e.g., including configuration changes to one or more slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N)). Master node <b>12</b>(<b>1</b>) may broadcast a NEW STRUCTURE WRITE command to substantially all slave nodes <b>12</b>(<b>1</b>)-<b>12</b>(N) and transition to a first state <b>104</b> STATE<b>1</b>. When master node <b>12</b>(<b>1</b>) transitions to first state <b>104</b> STATE<b>1</b>, a counter register may be loaded with a predetermined non-zero value (e.g., 3). While in first state <b>104</b> STATE<b>1</b>, the current count may be decremented upon receiving a broadcast acknowledgement (ACK) message from the last slave node <b>12</b>(N) and the value sent to the control frame. The broadcast acknowledgement may not be received by master node <b>12</b>(<b>1</b>) if the control frame does not pass a CRC check at last slave node <b>12</b>(N). The broadcast acknowledgement may not be accepted by master node <b>12</b>(<b>1</b>) if the response frame does not pass a CRC check at master node <b>12</b>(<b>1</b>). When the current count reaches 0, master node <b>12</b>(<b>1</b>) may transition to second state <b>106</b> STATE<b>2</b>. The NEW STRUCTURE may be applied at the end of the upstream transfer while in second state <b>106</b> STATE<b>2</b>.

0043In the slave node version of state machine <b>100</b>, each slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) may transition to first state <b>104</b> STATE<b>1</b> from initial state <b>102</b> STATE<b>0</b> on receiving a broadcast NEW STRUCTURE WRITE and the predetermined non-zero value (e.g., 3) may be loaded into a counter register. A broadcast NEW STRUCTURE WRITE with no CRC error may override the current count in first state <b>104</b> STATE<b>1</b>. In the absence of a valid broadcast NEW STRUCTURE WRITE, the current count may decrement in first state <b>104</b> STATE<b>1</b>. When the current count reaches zero, slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) may transition to second state <b>106</b> STATE<b>2</b>. The NEW STRUCTURE may be applied at the end of the upstream transfer while in second state <b>106</b> STATE<b>2</b>. In various embodiments, the control frame and/or response frame may be corrupted over more than the predetermined non-zero number (e.g., 3) of consecutive bus frames before the different nodes <b>12</b>(<b>1</b>)-<b>12</b>(N) are out of sync with each other.

0044Turning to <figref idref="DRAWINGS">FIG. 8</figref>, <figref idref="DRAWINGS">FIG. 8</figref> is a simplified logic diagram illustrating example details of an interrupt system <b>110</b> according to an embodiment of system <b>10</b>. Each node <b>12</b>(<b>1</b>)-<b>12</b>(N) may be capable of reporting various errors (e.g., CRC error, data parity error, data decode error, etc.) as interrupts to host controller <b>18</b>. Slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N) may send an interrupt request to master node <b>12</b>(<b>1</b>), which may signal host controller <b>18</b> through a dedicated interrupt pin. In various embodiments, the A²B protocol may include a distributed interrupt state machine, for example, to reduce interrupt overhead on host controller <b>18</b>. When an interrupt from one of slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N) is accepted by master node <b>12</b>(<b>1</b>), master node <b>12</b>(<b>1</b>) may signal the interrupt to host controller <b>18</b> as soon as possible.

0045When a new slave node interrupt is accepted, master node <b>12</b>(<b>1</b>) may perform a read of pertinent slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) to acquire details on the interrupt and may store the details locally on master node <b>12</b>(<b>1</b>). Master node <b>12</b>(<b>1</b>) may clear the interrupt in pertinent slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) automatically (e.g., without user or host controller intervention). Because of the interrupt state machine, host controller <b>18</b> may read two registers from master node <b>12</b>(<b>1</b>) to get substantially all of the details to handle the interrupt. One of the reads can also automatically clear the interrupt in master node <b>12</b>(<b>1</b>) so that writes are not required to clear any interrupt.

0046A²B Protocol engine <b>40</b> may include a set of registers that provide support for interrupts to host controller <b>18</b>. Example registers include INTSRC, INTTYPE, INTPND<b>0</b>, INTPND<b>1</b>, INTPDN<b>2</b>, INTMSK<b>0</b>, INTMSK<b>1</b>, and INTMSK<b>2</b>. An IRQ pin on master node <b>12</b>(<b>1</b>) may be used to signal an interrupt to host controller <b>18</b>. In an example embodiment, the IRQ pin can be cleared by a write of 1, and it may also be cleared on a host read of INTTYPE in master node <b>12</b>(<b>1</b>). Thus, a write may not be necessary to clear the interrupt.

0047In one example embodiment, the INTSRC and INTTYPE registers includes the details that host controller <b>18</b> may use to determine the cause of the interrupt. The INTSRC register can indicate whether the active interrupt was generated by master node <b>12</b>(<b>1</b>) or one of slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N), including the identifier (ID) of slave node <b>12</b>(<b>2</b>)-<b>12</b>(N) if any. When the IRQ pin is low or a pending interrupt has just been cleared and an interrupt is pending, priority logic may be used to determine the value to be written to the INTSRC register. The INTTYPE register may include additional details on the cause of the interrupt. When an interrupt generated by one of slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N) becomes active, master node <b>12</b>(<b>1</b>) may read the INTTYPE value from relevant one of slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N) and write the INTTYPE value into the INTTYPE register in master node <b>12</b>(<b>1</b>). Subsequently, master node <b>12</b>(<b>1</b>) may clear the interrupt source in the slave node <b>12</b>(<b>2</b>)-<b>12</b>(N).

0048Turning to <figref idref="DRAWINGS">FIG. 9</figref>, <figref idref="DRAWINGS">FIG. 9</figref> is a simplified graph <b>120</b> indicating comparisons of electromagnetic (EM) emissions with and without a scrambler according to embodiments of system <b>10</b>. EM emissions are plotted on the Y-axis against frequency on the X-axis. Line <b>122</b> indicates EM emissions with the scrambler, and line <b>124</b> indicates EM emissions without the scrambler. To reduce EM emissions, A²B protocol engine <b>40</b> may use scrambler <b>64</b>, which may be applied to a portion of the data transmitted by node <b>12</b>(<b>1</b>)-<b>12</b>(N). Substantially all of the data transmitted except for the preamble and a 2-bit frame count that follows the preamble may be scrambled in an example embodiment. In one specific embodiment, 1024 bits in a bus frame may be divided into a 64-bit control frame followed by downstream data and a 64-bit response frame followed by upstream data. The first 16 bits of the control frame and response frame (e.g., including the preamble and frame count) may not be scrambled. The remaining 48 bits of the control frame and response frame as well as any data being transmitted may be scrambled.

0049In one embodiment, scrambler <b>64</b> may use a 16-bit LFSR to generate a pseudo-random bit-stream. The LFSR may be based on polynomial G(x)=x¹⁶+x¹⁴+x¹³+x¹¹+1 (where x¹⁶represents the 16^thbit, x¹⁴represents the 14^thbit, x¹³represents the 13^thbit and x¹¹represents the 11^thbit). The LFSR also uses a different starting seed based on the 2-bit frame count so that a static data set may not cause a repeating pattern with an audio-rate frequency. The use of scrambler <b>64</b> may diffuse the EM emissions in the frequency domain as much as possible for a given data encoding method.

0050Turning to <figref idref="DRAWINGS">FIG. 10</figref>, <figref idref="DRAWINGS">FIG. 10</figref> is a simplified diagram illustrating compression <b>130</b> of 16 bit data <b>132</b> to 12 bit data <b>134</b> according to an embodiment of system <b>10</b>. A²B protocol engine <b>40</b> may provide optional data compression/decompression so that less bandwidth can be used on A²B twisted wire pair bus <b>14</b> at a given data size with better quality than the next lower data size. In one embodiment, 3 bits indicating a number of repeated sign bits in the number followed by a sign bit and N−4 bits of data may be transmitted in the compressed format, where N is the A²B data size.

0051In an example embodiment, the optional floating-point data compression in A²B protocol engine <b>40</b> can be used on 16-bit, 20-bit, or 24-bit audio data. The compression mechanism may reduce the data size by 4 bits for transmission over twisted wire pair bus <b>14</b> and the data is translated back before it is transmitted from the node (e.g., via a serial port). The compression is accomplished by encoding the number of leading sign bits into the first 3 bits of the compressed data field, placing the sign bit in the following position, and using the remainder of the compressed data field to store as many remaining data bits as possible. Depending on the size of the number being compressed, up to 6 least significant bits (LSBs) of the input data may be discarded.

0052Turning to <figref idref="DRAWINGS">FIG. 11</figref>, <figref idref="DRAWINGS">FIG. 11</figref> is a simplified diagram illustrating decompression <b>140</b> from 12 bit compressed data <b>142</b> to 16 bit decompressed data <b>144</b>. For decompression, the appropriate numbers of sign bits are placed in the most significant bits (MSBs) of the output followed by one bit, which is the inverse of the sign bit. The remaining data is placed after the inverse sign bit and any non-received bits are filled with the inverse of the LSB of the compressed data. Hence, decompressed data can be evenly distributed and may have no DC offset compared to the input.

0053Turning to <figref idref="DRAWINGS">FIG. 12</figref>, <figref idref="DRAWINGS">FIG. 12</figref> is a simplified flow diagram illustrating example operations <b>150</b> that may be associated with an embodiment of system <b>10</b>. At <b>152</b>, master node <b>12</b>(<b>1</b>) may generate clock, synchronization and framing signals in two-wire communication protocol (A²B protocol). At <b>154</b>, A²B protocol engine <b>40</b> may facilitate bi-directional transfer of data using twisted wire pair bus <b>14</b> to connect each node to the next node. At <b>156</b>, A²B protocol engine <b>40</b> may synchronize updates of configuration data using state machine <b>100</b>. At <b>158</b>, master node <b>12</b>(<b>1</b>) may power slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N) over twisted wire pair bus <b>14</b>. At <b>160</b>, master node <b>12</b>(<b>1</b>) may transmit the control frame and downstream data from master node <b>12</b>(<b>1</b>) in downstream portion of the two-wire communication protocol. At <b>162</b>, master node <b>12</b>(<b>1</b>) may receive the response frame and upstream data from slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N) in upstream portion of the two-wire communication protocol.

0054Turning to <figref idref="DRAWINGS">FIG. 13</figref>, <figref idref="DRAWINGS">FIG. 13</figref> is a simplified flow diagram illustrating example operations <b>170</b> that may be associated with an embodiment of system <b>10</b>. At <b>172</b>, state machine <b>100</b> transitions to a first state <b>104</b> upon master node <b>12</b>(<b>1</b>) broadcasting a new structure write command to plurality of slave nodes <b>12</b>(<b>2</b>)-<b>12</b>(N). At <b>174</b>, a counter may be set to a predetermined non-zero value (e.g., 3). At <b>176</b>, the counter may be decremented upon receipt of acknowledgement from last slave node <b>12</b>(N). At <b>178</b>, state machine <b>100</b> may transition to second state <b>104</b> when the counter reaches zero. At <b>180</b>, the new structure may be applied while state machine <b>100</b> is in second state <b>104</b>.

0055Turning to <figref idref="DRAWINGS">FIG. 14</figref>, <figref idref="DRAWINGS">FIG. 14</figref> is a simplified flow diagram illustrating example operations <b>190</b> that may be associated with an embodiment of system <b>10</b>. At <b>192</b>, master node <b>12</b>(<b>1</b>) receives an interrupt from one of slave nodes <b>12</b>(<b>1</b>)-<b>12</b>(N). At <b>194</b>, master node <b>12</b>(<b>1</b>) may signal the interrupt to host controller <b>18</b>. At <b>196</b>, master node <b>12</b>(<b>1</b>) may read the slave node to acquire details on the interrupt. At <b>198</b>, master node <b>12</b>(<b>1</b>) stores details of the interrupt locally in master node <b>12</b>(<b>1</b>). At <b>200</b>, master node <b>12</b>(<b>1</b>) may automatically clear the interrupt in the slave node. Going back to <b>194</b>, at <b>210</b>, host controller <b>18</b> may read two registers on master node <b>12</b>(<b>1</b>) to retrieve details of the interrupt. At <b>220</b>, one of the reads may automatically clear the interrupt in master node <b>12</b>(<b>1</b>).

0056Note that in this Specification, references to various features (e.g., elements, structures, modules, components, steps, operations, characteristics, etc.) included in “one embodiment”, “example embodiment”, “an embodiment”, “another embodiment”, “some embodiments”, “various embodiments”, “other embodiments”, “alternative embodiment”, and the like are intended to mean that any such features are included in one or more embodiments of the present disclosure, but may or may not necessarily be combined in the same embodiments.

0057In the discussions of the embodiments above, the capacitors, clocks, DFFs, dividers, inductors, resistors, amplifiers, switches, digital core, transistors, and/or other components can readily be replaced, substituted, or otherwise modified in order to accommodate particular circuitry needs. Moreover, it should be noted that the use of complementary electronic devices, hardware, software, etc. offer an equally viable option for implementing the teachings of the present disclosure.

0058In one example embodiment, any number of electrical circuits of the FIGURES may be implemented on a board of an associated electronic device. The board can be a general circuit board that can hold various components of the internal electronic system of the electronic device and, further, provide connectors for other peripherals. More specifically, the board can provide the electrical connections by which the other components of the system can communicate electrically. Any suitable processors (inclusive of digital signal processors, microprocessors, supporting chipsets, etc.), memory elements, etc. can be suitably coupled to the board based on particular configuration needs, processing demands, computer designs, etc. Other components such as external storage, additional sensors, controllers for audio/video display, and other peripheral devices may be attached to the board as plug-in cards, via cables, or integrated into the board itself.

0059In another example embodiment, the electrical circuits of the FIGURES may be implemented as stand-alone modules (e.g., a device with associated components and circuitry configured to perform a specific application or function) or implemented as plug-in modules into application specific hardware of electronic devices. Note that particular embodiments of the present disclosure may be readily included in a system on chip (SOC) package, either in part, or in whole. An SOC represents an IC that integrates components of a computer or other electronic system into a single chip. It may contain digital, analog, mixed-signal, and often radio frequency functions: all of which may be provided on a single chip substrate. Other embodiments may include a multi-chip-module (MCM), with a plurality of separate ICs located within a single electronic package and configured to interact closely with each other through the electronic package. In various other embodiments, the functionalities as described herein may be implemented in one or more silicon cores in Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and other semiconductor chips.

0060It is also imperative to note that all of the specifications, dimensions, and relationships outlined herein (e.g., the number of components, logic operations, etc.) have only been offered for purposes of example and teaching only. Such information may be varied considerably without departing from the spirit of the present disclosure, or the scope of the appended claims. The specifications apply only to one non-limiting example and, accordingly, they should be construed as such. In the foregoing description, example embodiments have been described with reference to particular component arrangements. Various modifications and changes may be made to such embodiments without departing from the scope of the appended claims. The description and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.

0061Note that the activities discussed above with reference to the FIGURES are applicable to any integrated circuits that involve signal processing, particularly those that rely on synchronization signals to execute specialized software programs, or algorithms, some of which may be associated with processing digitized real-time data. Certain embodiments can relate to multi-DSP signal processing, floating point processing, signal/control processing, fixed-function processing, microcontroller applications, etc. In certain contexts, the features discussed herein can be applicable to medical systems, scientific instrumentation, wireless and wired communications, radar, industrial process control, audio and video equipment, current sensing, instrumentation (which can be highly precise), and other digital-processing-based systems.

0062Moreover, certain embodiments discussed above can be provisioned in digital signal processing technologies for medical imaging, patient monitoring, medical instrumentation, and home healthcare. This could include pulmonary monitors, accelerometers, heart rate monitors, pacemakers, etc. Other applications can involve automotive technologies for safety systems (e.g., stability control systems, driver assistance systems, braking systems, infotainment and interior applications of any kind). Furthermore, powertrain systems (for example, in hybrid and electric vehicles) can apply the functionalities described herein in high-precision data conversion products in battery monitoring, control systems, reporting controls, maintenance activities, etc.

0063In yet other example scenarios, the teachings of the present disclosure can be applicable in the industrial markets that include process control systems that help drive productivity, energy efficiency, and reliability. In consumer applications, the teachings of the electrical circuits discussed above can be used for image processing, auto focus, and image stabilization (e.g., for digital still cameras, camcorders, etc.). Other consumer applications can include audio and video processors for home theater systems, DVD recorders, and high-definition televisions. Yet other consumer applications can involve advanced touch screen controllers (e.g., for any type of portable media device). Hence, such technologies could readily part of smartphones, tablets, security systems, PCs, gaming technologies, virtual reality, simulation training, etc.

0064Note that with the numerous examples provided herein, interaction may be described in terms of two, three, four, or more electrical components. However, this has been done for purposes of clarity and example only. It should be appreciated that the system can be consolidated in any suitable manner. Along similar design alternatives, any of the illustrated components, modules, and elements of the FIGURES may be combined in various possible configurations, all of which are clearly within the broad scope of this Specification. In certain cases, it may be easier to describe one or more of the functionalities of a given set of flows by only referencing a limited number of electrical elements. It should be appreciated that the electrical circuits of the FIGURES and its teachings are readily scalable and can accommodate a large number of components, as well as more complicated/sophisticated arrangements and configurations. Accordingly, the examples provided should not limit the scope or inhibit the broad teachings of the electrical circuits as potentially applied to a myriad of other architectures.

0065Numerous other changes, substitutions, variations, alterations, and modifications may be ascertained to one skilled in the art and it is intended that the present disclosure encompass all such changes, substitutions, variations, alterations, and modifications as falling within the scope of the appended claims. In order to assist the United States Patent and Trademark Office (USPTO) and, additionally, any readers of any patent issued on this application in interpreting the claims appended hereto, Applicant wishes to note that the Applicant: (a) does not intend any of the appended claims to invoke paragraph six (6) of 35 U.S.C. section 112 as it exists on the date of the filing hereof unless the words “means for” or “step for” are specifically used in the particular claims; and (b) does not intend, by any statement in the specification, to limit this disclosure in any way that is not otherwise reflected in the appended claims.

OTHER NOTES, EXAMPLES, AND IMPLEMENTATIONS

0066Note that all optional features of the apparatus described above may also be implemented with respect to the method or process described herein and specifics in the examples may be used anywhere in one or more embodiments. In a first example, a system is provided (that can include any suitable circuitry, dividers, capacitors, resistors, inductors, ADCs, DFFs, logic gates, software, hardware, links, etc.) that can be part of any type of computer, which can further include a circuit board coupled to a plurality of electronic components. The system can include means for generating clock, synchronization and framing signals in a two-wire communication protocol for the plurality of slave nodes; means for facilitating bi-directional transfer of data using a twisted wire pair bus to connect each node to the next node; means for synchronizing updates of configuration data using a state machine; means for powering the slave nodes over the twisted wire pair bus; means for transmitting a control frame and downstream data from the master node in a downstream portion of the two-wire communication protocol, where a synchronization pattern at a beginning of the control frame is used as a time base by each slave node; and means for receiving a response frame and upstream data from the slave nodes in an upstream portion of the two-wire communication protocol.

0067The system can also include means for transitioning to a first state upon broadcasting a new structure write to the plurality of slave nodes; means for setting a counter to a predetermined non-zero value; means for decrementing the counter upon each acknowledgement received from the plurality of slave nodes; means for transitioning to a second state when the counter reaches zero; and means for applying the new structure while in the second state. The system can further include means for receiving an interrupt from a slave node; means for signaling the interrupt to a host controller; means for reading the slave node to acquire details on the interrupt; means for storing the details locally on the master node; and means for clearing the interrupt in the slave node automatically.

0068The ‘means for’ in these instances (above) can include (but is not limited to) using any suitable component discussed herein, along with any suitable software, circuitry, hub, computer code, logic, algorithms, hardware, controller, interface, link, bus, communication pathway, etc. In a second example, the system includes memory that further comprises machine-readable instructions that when executed cause the system to perform any of the activities discussed above.