Patent Application
20060067212
Communication protocols provide devices with an agreed-upon format that allows for transmission of data between the devices. Many communication protocols transmit and receive data at a predetermined speed or transfer rate. Furthermore, communication protocols may be limited to communications between only two devices. In other words, a particular device may not be able to communicate at a single instance to multiple devices.
The following detailed description refers to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure (Fig.) in which the reference number first appears. Moreover, the same reference numbers are used throughout the drawings to reference like features and components.
Overview
The following discussion is directed to systems and methods for communication between a master and one or more token devices using a communication protocol that accommodates for the slowest token device.
Exemplary Communication System Environment
Master device 105 includes a token device identifier table 137 which identifies token devices 110-135 by unique identifier numbers as provided by master device to each of token devices 110-135. The identifier numbers are assigned to and provided to the token devices 110-135 using the described communication protocol below. The identifier numbers may be subsequently changed by the master device 105.
In this example, two way communication takes place between master device 105 and token devices 110-135, such that master device 105 sends (i.e., writes to) and receives (i.e., reads from) token devices 110-135. In other implementations, token devices 110-135 communicate with one another. Specifically, token device 110 communicates with master device 105 through communication path 140. Likewise token device 115 uses communication path 145; token device 120 uses communication path 150; token device 125 uses communication path 155; token device 130 uses communication path 160; and token device 135 uses communication path 165. Communication paths 140-165 may be wireless or wired. Wireless implementations of communications paths 140-165 may make use of several technologies which include infra-red (IR) and radio frequency (RF) transmission technology.
Device 200 includes a processor 205 to process various instructions to control operation of device 200, including processing of instructions stored in a memory 210. Furthermore, processor 205 is used to communicate with other devices, and particularly communicate using the communication protocol described below. In other embodiments, an application specific integrate circuit (ASIC) may be implemented which may or may not include a processor.
Memory 210 stores instructions or data structures that implement the communication protocol described below and may store other instructions and applications. Memory 210 further may store identifier numbers of token device which may be in the form of a database or table such as table 137 of
Device 200 further includes a communication interface 215 used to pass and receive communications or data between device 200 and other devices. For wireless RF communications, communication interface 215 may include an antenna, an analog to digital (AD) converter, and a digital to analog (DA) converter. For wireless IR communications, communication interface 215 may include an IR sensor and receiver, an AD converter, and a DA converter. For wired communications, communication interface 215 may make use of one or more of several communication standards such as universal serial bus, parallel port, and other industry and/or proprietary wired interface standards.
A clock 220 is included that provides a clock signal having a particular frequency or rate at which bits (digital words) processed using the described communication protocol are transmitted from device 200. Clock 220 may be a general purpose clock that provides timing for device 200.
In particular implementations, a token device may not have a clock signal which determines when a bit is transmitted, and clock 220 is therefore not included in such a token device. In these implementations, the token device waits for a bit to be received from the master prior to sending its bit—such as in a full-duplex transmission. The bit transmission may be event driven by the master. Each bit signal transition from the master triggers a bit from the token device to be sent.
In this example, a systems bus 225 connects processor 205, memory 210 and communication interface 215, clock 220, and other components (not shown) that are included in device 200. Systems bus 225 receives and sends communication (i.e., data, commands, and instructions) from processor 205, memory 210, and communication interface 215. Systems bus 225 receives the clock signal from clock 220.
In this example, a bit representing “1” is seen as bit 300. Bit 300 starts with a high logic value followed (transitioned) to a low logic value. A bit representing a “0” starts with a low logic value followed (transitioned) to a high logic value. Word 310 is an example of a bit word that uses the described bi-phase encoding, and represents the digital word “1101”.
A master device, such as master device 105, initiates a start sequence by transmitting a unique data or bit pattern. The bit pattern may not be bi-phase coded. In other words a logic value of “0” such as bits 405 and 410 is simply a low value. In this example, bit 405 is a previous stop bit followed by start bit 410.
In one embodiment, the unique bit pattern that is recognized by a receiving token device is sent as a series of four high logic values (e.g., four “1” bits) as represented by bits 415, followed by a low logic value (e.g., one “0” bit) as represented by bit 420. A subsequent high logic value 425 that follows bit 420 indicates the start of data transmission from the master device.
In one embodiment, a valid start is determined when a ratio of two low logic values and five high logic values are received by a token device. In other words, if a token device determines that there are more than two low logic values for every five high logic values, it is not a valid start. The use of bi-phase encoding is particularly not used, since bi-phase encoding may have up to two cycles at the same logic level. Therefore bi-phase encoding is not used in order to allow token devices to distinguish a start.
In one embodiment, the master device initially transmits the bits at the lowest possible rate that a potential token device may receive. As discussed below, the transfer rate may be increased after the master device receives a similar speed sequence bit pattern from the token device.
In one embodiment, the speed sequence or rate is determined by the token device by accounting for the time in receiving the four high cycles and one low cycle (or a total of five cycles). In other words, the rate or speed is five cycles divided by the time in which four high bits and one low bit are received. The logic value is the initial speed sequence.
In embodiments where a token device does not have an identifier number that is recognized by the master device, the token device may be identified as a zero (“0”). The master device when looking for new token devices may broadcast device identifier of zero (“0”) in order for new devices to respond back to the master device. Token devices initially have an identifier of “0”, and if not addressed for a time by the master device, regardless of the identifier they have, go back (change) to identifier “0”.
A high bit 500 (which may be bit 425 of
The end of the start identifier transmission may be left at a high or low state; however, after the last cycle, the transmission transitions to a low state. A stop sequence or stop transmission may be indicated by four consecutive low state cycles. In this embodiment, bi-phase coding may not be used for the stop sequence.
The receiving token device responds back to the master device by sending an acknowledge bit 515. The acknowledge bit 515 is sent for at least one cycle in order for the master device to recognize the acknowledge bit 515. The master device responds to acknowledge bit 515 with an acknowledge check bit 520—the acknowledge bit 515 being sampled on the falling edge of the acknowledge check bit 520 by the master device. In certain cases, the acknowledge bit 515 may be a speed sequence bit transmission that is described below. As further described below, the speed sequence bit transmission from the token device allows the master device to readjust its bit rate transmission to increase the bit rate transmission of the token device.
If transmission is to be stopped, a stop sequence or four logic low values may be transmitted instead of an acknowledge bit 515.
In this example, the command sequence transmission is an eight bit word or a byte word. The MSB is bit 605 which is transmitted first. If a logic value of “1” is provided at bit 605, it indicates a standard command that is reserved and is recognized by all token devices. If the logic value at bit 605 is “0” it is a command that may be created by a user or unique to specific token devices.
Bit 610 defines whether a write or a read is to be performed. A logic value of “0” indicates a read or a transmission of data from master device to token device(s). A logic value of “1” indicates a write or a reception of data from token device(s) to the master device.
A 6-bit command word 615 follows bit 610, where command word 615 represents various commands or instructions. Examples of instructions include “Do Nothing”, “Send Device ID”, “Send Vendor ID”, “Set Family ID”, etc.
In certain situations, a data bit sequence transmission as described below is performed by the master device that broadcasts a time-stamp to token devices. This time-stamp broadcast may be sent to all eligible token devices. Token devices having an out of date time stamp may be reset in order for the master device to identify them. In other words, the scenario is the master device sends out a general broadcast—no particular device or family is identified (i.e., identifier bits set to DC), and the token devices (i.e., token devices with out of date time-stamps) are requested to send back their identifier numbers to the master devices. In other words, the master device sends a command using the command sequence bit stream, instructing token devices that are identified as having out of date time-stamps. The command is sent to specific token devices, or groups of token devices. If a token device determines that the identifier byte is not for them, it does not have to listen anymore. For example, with less than 16 transmissions, 16 token devices in a group can be group addressed and have their time stamp updated. Then with less than 16 transmissions all token devices can have their time stamp checked. If the time stamp doesn't match, a token device will set its device id to “0” and be re-instantiated by the master device.
The receiving token device responds back to the master device by sending an acknowledge bit 620. The acknowledge bit 620 is sent for at least one cycle in order for the master device to recognize the acknowledge bit 620. The master device responds to acknowledge bit 620 with an acknowledge check bit 625—the acknowledge bit 620 being sampled on the falling edge of the acknowledge check bit 625 by the master device.
If transmission is to be stopped, a stop sequence or four logic low values may be transmitted instead of an acknowledge bit 620.
In this embodiment, data word 705 may be an eight bit word or byte word which token devices should be able to receive and transmit in order for clients to respond to commands and start sequence transmissions from the master device. Data word 705 may be set to accommodate greater word lengths (e.g. such as 16, 32, and 64 bit words) depending on capability of master and token devices. The MSB of data word 705 is transmitted first.
In order to verify that the token device has received the data, the token device responds back to the master device by sending an acknowledge bit 710. The acknowledge bit 710 is sent for at least one cycle in order for the master device to recognize the acknowledge bit 710. The master device responds to acknowledge bit 710 with an acknowledge check bit 715—the acknowledge bit 710 being sampled on the falling edge of the acknowledge check bit 715 by the master device.
If transmission is to be stopped, a stop sequence or four logic low values may be transmitted instead of acknowledge bit 710.
The speed sequence bit transmission is similar to the speed sequence bit transmission transcribed above that a master device transmits to a token device, and likewise may not be bi-phase coded.
In one embodiment, the speed sequence bit transmission includes a unique bit pattern of four high logic values (e.g., four “1” bits) (e.g., four “1” bits) as represented by bits 800, followed by a low logic value (e.g., one “0” bit) as represented by bit 805. The speed sequence bit transmission may be used by the master device to determine the bit rate at which the token device is transmitting. Knowing the actual bit rate at which the token device is transmitting allows the master device to adjust, such as increase, its bit rate transmission if applicable.
In one embodiment, the speed sequence or rate is determined by the master device by accounting for the time in receiving the four high cycles and one low cycle (or a total of five cycles). In other words, the rate or speed is five cycles divided by the time in which four high bits and one low bit are received. The master device may then adjust for the actual calculated speed sequence.
The token device data sequence bit transmission is particularly sent when a command bit sequence transmission is sent by the master device which indicates a read. In reference to
The master device responds back to the token device with an acknowledge bit and the token device responds with an acknowledge check bit. If the master device desires to stop transmission the master device sends a stop sequence of four logic low values instead of an acknowledge bit. If the token device desires to stop transmission the token devices sends a stop sequence of four logic low values instead of any subsequent data sequence bit transmission.
This example shows an acknowledge sequence for a multiple write (i.e., master sends data) transmission. Acknowledge check bits 900, 905, 915, and 920 are transmitted by the master device in response to acknowledge bits that are transmitted by multiple token devices. In this example a token device “0” transmits an acknowledge bit 925; a token device “1” transmits an acknowledge bit 930; and a token device “N” transmits an acknowledge bit 925.
Acknowledge check bits 900-920 are given a time slot to respond to their respective acknowledge bits, where acknowledge bits 925-935 are given a time slot to be transmitted by their respective token devices. The acknowledge bits 925-935 are checked on the falling edge of their respective acknowledge check bits 900-920. Alternatively, acknowledge may be driven by events—the master device asserts an acknowledge check, waits for a token device to send an acknowledge bit, pulls its line to a low logic state, waits one cycle, pulls its line to a high logic state for a succeeding acknowledge bit. Acknowledge based on events is not viable, if a token at an address which the master device is communicating to, does not exist.
When the multiple acknowledge sequence is complete, the master may transmit at a single instance a command bit sequence or a data bit sequence to all token devices that have successfully completed the acknowledge sequence.
In one embodiment, when performing a multiple read (i.e., master receives data), each token device is allowed to send its data prior to the master device, prior to subsequent token devices sending their data to the master device. Acknowledgement sequence is performed as described above when a single token device communicates with the master device.
The process 1000 is illustrated as a collection of blocks in a logical flow graph, which represent a sequence of operations that can be implemented in hardware, software, or a combination thereof. In the context of software, the blocks represent computer instructions that, when executed by one or more processors, perform the recited operations. The process 1000 is described with reference to master device 105 and token devices 110-135 of
At block 1005, master device 105 transmits (initiates) an initial speed sequence bit pattern that includes four high logic values, followed by one low logic value. A start identifier sequence identifying a particular token device or devices is transmitted after the speed sequence. Initially, when token devices have not been identified by the master device 105, a general broadcast is transmitted which all token devices are able to receive. Unidentified token devices may be given an identification number of zero (“0”) and later through a command and data bit sequence from the master device 105 be given a unique identifier number.
At block 1010, one or more token devices 110-135 transmit an acknowledge bit upon receipt of the speed sequence and start identifier bit sequence from master device 105. Master device 105 performs an acknowledge check by transmitting an acknowledge check bit.
At block 1015, the master device 105 sends a command bit sequence to be read by token devices 110-135 as identified by the start identifier sequence at block 1005. Command bit sequences may include a start, an identifier, and command data. Write commands may or may not contain data packets. When initiating or when token devices do not have a particular identifier number the command bit sequence may be to receive a particular identifier number which the master device tracks (e.g., keeps in a reference table such as table 137 of
At block 1020, the identified token device or devices 110-135 reads the transmitted command and replies with an acknowledge bit that the command was received. Master device 105 performs an acknowledge check by transmitting an acknowledge check bit.
Commands from the master device 105 may be write (i.e., send data) or read (i.e., receive data). For read commands (i.e., following the “NO” branch of block 1025) there may or may not be data to be sent from the token device. If data is to be sent (i.e., following the “YES” branch of block 1030), the command instructs the identified token device or devices to send data or perform block 1035. Block 1035 further provides that after the data bit sequence, that the token device or devices 110-135 send either a succeeding data bit sequence or a stop sequence (e.g. four logic low values).
If no data is to be sent (i.e., following the “NO” branch of block 1030), transmission may end. If transmission is to be stopped (i.e., following the “YES” branch of block 1040), at block 1045, the master device performs a stop sequence by transmitting four logic low values. If transmission is to continue (i.e., following the “NO” branch of block 1040), a subsequent command bit sequence is sent from the master device (i.e., block 1015 is performed).
At block 1055, the master device 105 replies with a acknowledge bit indicating it has received the data bit sequence from the token device or devices 110-135. The token device or devices 110-135 may perform an acknowledge check by transmitting an acknowledge check bit. Transmission may or may not end afterwards (i.e., block 1040).
If a command is a write (i.e., following the “YES” branch of block 1025), the master device sends a data bit sequence to the token device or devices 105-135 or performs block 1055.
One or more than one (multiple) of token devices 105-135 may receive the data bit sequence from the master device. If multiple token devices receive the data bit sequence (i.e., following the “YES” branch of block 1060), at block 1065, each of the multiple token devices replies with an acknowledge bit per an allocated time slot, until all token devices have had an opportunity to reply. The master device may perform an acknowledge check by transmitting acknowledge check bits per each acknowledge bit transmitted by the token devices. The master device then determines if transmission is to be stopped or continued (i.e., block 1040).
If a single token device receives the data bit sequence (i.e., following the “NO” branch of block 1025), at block 1070, the token device replies with an acknowledge bit. The master device may perform an acknowledge check by transmitting acknowledge check bit. The master device then determines if transmission is to be stopped or continued (i.e., block 1040).
This described protocol may also be a physical layer of a more complicated protocol. Transmitted data may be encrypted, include a parity or checksum byte added, or encoded in another method that is unique to a token device. The physical layer provides all the basic functionality for communications without using a large protocol stack for communications with simpler devices.
Although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter of the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claimed subject matter.
