JP3489287B2 - Data exchange method by serial bus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data exchange system for a serial data bus in a microcomputer system. 2. Description of the Related Art In a microcomputer system, methods for exchanging data with an input / output device include a data exchange method using a parallel bus and a data exchange method using a serial bus. The serial bus is a bus for serially exchanging data in synchronization with a clock, such as a two-wire bus which is a data line and a clock for taking in data from the data line. FIGS. 6 to 10 show an example in which data is exchanged between a microcomputer and a data input / output device in a data format including an ID (address), a command, read / write data, and a data checker. Show. [0004] As shown in FIGS. 7 and 9, a microcomputer 1 and each input / output device 3 are connected by a serial bus 2, and downlink data for transmitting data from the microcomputer 1 to a certain input / output device 3. As shown in FIG. 6, the format consists of 39 bits of ID (address) 16 bits, command 3 bits, read / write data 16 bits and data checker 4 bits. Output data to The command is a read operation from the microcomputer when the command is 101, a write operation from the microcomputer when 110, and the command is invalid in other cases. When data is sent from the input / output device 3 to the microcomputer 1, the upstream data format is 16 bits for ID (address), 3 bits for response code, 16 bits for read / write data as shown in FIG. It consists of 39 bits of 4 bits and a data checker, and outputs data to the serial bus 2 in the order of 1 to 39. When the command is 001, the response code to the read command from the microcomputer is set. When the command is 010, the response code to the write command from the microcomputer is invalid. [0006] The operation of the data exchange system is performed as follows. (1) In order to perform a read / write operation on the input / output device 3 with the microcomputer 1,
Outputs data to serial bus 2. In the case of a read operation, the data is output to the serial bus in the order of the ID (address) of the input / output device, the command, and the data checker. In the case of a write operation, the serial bus 2 is used in the order of ID (address), command, write data, and data checker.
Output to (2) The input / output device 3 which has received the 39-bit data from the microcomputer 1 from the serial bus 2 performs ID (address) match / mismatch and serial data check, and all pass. In this case, a read / write operation is performed on the input / output device 31. If the check fails, the read / write operation is not performed. (3) The input / output device 3 that has performed the read / write operation on the input / output device 31 performs, in the case of the read operation, its own ID (address), response code, read device, and data checker order. Output data to the serial bus. In the case of a write operation, data is output to the serial bus 2 in the order of its own ID (address), response code, write data, and data checker. (Write data feedback) (4) The microcomputer 1 receives serial data from the input / output device 3 from the serial bus 2. In the case of the present serial bus of the two-wire system, the data exchange system is a half-duplex system. When the data exchange of the 39-bit width described above is performed, when the clock of the serial bus is set to 1 MHz, 39 × 1 μS × 2 + α = 78 + α μS As described above, 78 + αμS (α: from the input / output device of the input / output device) (Overhead time due to read / write operation). In the case of a two-wire serial bus, when a microcomputer performs a read / write operation on an input / output device, data is exchanged because of a half-duplex system. It takes twice as long as the data bit width, resulting in a very inefficient device. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a serial bus in which a 4-wire serial bus can be used and the serial bus can be used efficiently. To provide a data exchange method using The serial bus exchange system of the present invention is a serial bus data exchange system for exchanging data between a microcomputer and each input / output device via a serial bus. Is divided into a serial bus for exclusive use of downlink for sending data from the microcomputer to the input / output device and a serial bus for exclusive use of uplink for sending data from the input / output device to the microcomputer.
And a line type, address the input and output device side from the downlink system serial bus, upon receiving the command, the response address to the upstream system serial bus, to give so that without the output of the response code, input and output apparatus at the same time while receiving data from the downlink system serial bus, the data exchange method according to the serial bus to obtain so that outputs data to the upstream system serial bus, the upstream system data format Li
Insert an error flag after load / write data,
Data and commands in the data format
Insert a data checker after the data and read
/ Insert a data checker after the write data,
Data, command data and write data.
Data can be checked independently of each other
Make sure each data check is consistent
Sometimes, response data is output to the upstream serial bus.
Start input, address data, command data part
Data check is OK, write data
When a data check error occurs,
Turn on the error flag during formatting and respond
It is like that. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 (FIGS. 1 to 4) As shown in FIG. 4, a serial bus 2 is connected from a microcomputer 1 to an input / output device 3 by a downstream serial bus 2 _1.
And separated from the input and output device 3 to the upstream system serial bus 2 ₂ to the microcomputer 1, and a full-duplex. The data format is a data format of the downstream system output from the microcomputer shown in FIG.
As shown in FIG. 2, ID (address) 16 bits, command 2 bits, read / write data 16 bits, downlink system,
It has a 39-bit configuration of 1 undefined bit and 4 bits of data checker for making the data width of the upstream system the same 39 bits. Data is output to the serial bus in the order of Nos. 1-39. When the command is 01, a read operation from the microcomputer is performed. When the command is 10, a write operation from the microcomputer is disabled. The data at the time of reading is dummy data. As shown in FIG. 2, the uplink data format output from the input / output device is 16 bits for ID (address), 2 bits for response code, 16 bits for read / write data, 1 bit for error flag, and data checker. A 4-bit 39-bit configuration was used. Data is output to the serial bus in the order of Nos. 1-39. When the command is 01, the response code of the read operation from the microcomputer is 10; when the command is 10, the response code of the write operation from the microcomputer is invalid; The data at the time of writing is feedback of write data. When the input / output device 3 receives data up to the 23rd bit of the downlink data format, it starts to output uplink data. In other words, from 24 to
16-bit reception operation at the 39th bit and 1
The 16-bit transmission operations up to the 16th bit overlap. In order to make the data widths of the downstream and upstream systems the same (39 bits), in this example, one undefined bit is inserted into the downstream data format. FIG. 3 shows an example of the protocol. Next, the operation of this embodiment will be described. (1) In order to perform a read / write operation on the input / output device 3 with the microcomputer 1,
And it outputs the data to the serial bus 2 ₁ of the downstream system. In the case of a read operation, the data is output to the downstream serial bus in the order of the ID (address) of the input / output device, the command, and the data checker. In the case of a write operation, ID (address),
The command, write data, and data checker are output to the downstream serial bus in this order. (2) The input / output device 3 receiving the ID (address) and command from the microcomputer from the downstream serial bus examines that the IDs match, and if they match, responds to the command. Start operation. [0020] In the case of the read operation: input and output device 3, starts to output your ID, and the downlink system serial bus 2 ₁ command. In addition, a read operation is performed on the input / output device to capture data. Data capture time from the input and output device 31, to complete in a few microseconds, may comprise a read data while outputting ID, and the command to the serial bus 2 ₂ uplink system. When the output of the ID and the command to the upstream serial bus is completed, the read data, the error flag, and the data checker are continuously output to the upstream serial bus. (Error flag:
A flag indicating whether or not a data check error has occurred when receiving data from the downstream serial bus.) In the case of a write operation: the input / output device transmits its own ID and command to the upstream serial bus. Start output. After receiving the write data and the data checker from the downstream serial bus, it confirms that there is no data error, and outputs the write data to the input / output device. When a data error occurs, no write data is output to the input / output device. After outputting the ID and command to the upstream serial bus,
Outputs write data, error flag, and data checker. (3) The microcomputer receives serial data from the input / output device from the upstream serial bus. By using a serial bus full-duplex system (four-wire system), when data exchange of 39 bits width is performed,
When the clock of the serial bus is 1 MHz, 39 × 1 μS + (39−16) × 1 μS = 62 μS where 39: Downstream bit width (39-16): Upstream bit width−Overlapping bit width with downstream system As described above, assuming that the uplink and downlink overlap bit widths are 16 bits, the read / write operation is completed in 62 μS. Second Embodiment (FIG. 5) In the method of the first embodiment, the data check is performed after all downlink data is received.
If D (address) data alone is not data checked) and the ID is garbled,
There is a response from the input / output device that the unit does not expect. " Also, depending on the location (physical) where the data corruption has occurred, it is conceivable that "there is a response from a plurality of input / output devices". Embodiment 2
Is to insert a data checker after ID data and command data in the data format of the downstream system (microcomputer unit → input / output device) so as to prevent the above-mentioned trouble or the like from occurring. As shown in FIG. 5, a data checker for the ID data and command data portion and a data checker for the write data portion are provided. As a result, "ID
"Data, command data" and "write data" can be checked independently of each other. When the input / output device receives the ID data and the command data and the ID match and the data check consistency are confirmed, the upstream system (input / output device → computer /
Unit) starts outputting response data to the serial bus. (No response if an error is found in the data check.) If the data check in the ID data and command data portions is OK and the data check error occurs in the write data portion, the input / output device is turned on. Without writing data to the output device,
Turns on the error flag during formatting and responds. In the downlink data format shown in FIG.
The command is a read operation from the microcomputer when the command is 01, a write operation from the microcomputer when 10 is the command, and invalid otherwise. The data at the time of reading is
This is dummy data. As described above, since the downstream data format as shown in FIG. 5 is used, the serial bus can be efficiently used without any problem by the protocols and access procedures as shown in FIGS. Since the present invention is configured as described above, the following effects can be obtained. (1) The serial bus is made into a 4-wire system and divided into an upstream serial bus and a downstream serial bus, and the serial bus is configured as a full-duplex system. When a read / write operation is performed on an input / output device via the bus, a bus access operation can be performed more efficiently than a two-wire serial bus. (2) By inserting a data checker after ID data and command data in the downlink data format, "ID data and command data"
And "write data" in independent data,
You can check. When the input / output device receives the ID data and the command data from the downstream serial bus output from the microcomputer unit and the ID matches and the data check is consistent, the data is output. Output of response data to the serial bus of the system can be started without any problem. If the ID is garbled data, there may be a problem such as "the computer unit has a response from an input / output device that is not expected" or a location (physical) where the garbled data occurs. There is a response. "

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a configuration of a downlink data format according to a first embodiment of the present invention. FIG. 2 is a configuration explanatory diagram of the same uplink data format. FIG. 3 is an explanatory diagram of the same protocol. FIG. 4 is an explanatory diagram of an access procedure. FIG. 5 is a diagram illustrating a configuration of a downlink data format according to the second embodiment; FIG. 6 is a diagram illustrating the configuration of a conventional downlink data format. FIG. 7 is an explanatory diagram of a downlink data access procedure. FIG. 8 is an explanatory diagram of a configuration of an uplink data format. FIG. 9 is an explanatory diagram of an uplink data access procedure. FIG. 10 is an explanatory diagram of the same protocol. [Description of Reference Numerals] 1 ... microcomputer 2 ... serial bus 2 ₁ ... downlink system serial bus 2 ₂ ... up system serial bus 3 ... output device 3 ₁ ... input-output device

Claims (1)

(1) A data exchange method using a serial bus for exchanging data between a microcomputer and each input / output device through a serial bus, wherein the serial bus is connected from the microcomputer to the input / output device side The dedicated serial bus for sending data to the microcomputer and the serial bus for sending data from the input / output device to the microcomputer are divided into 4-wire systems. at the time when the received response address to the upstream system serial bus, to give so that without the output of the response code, at the same time while receiving data from the downlink system serial bus input and output apparatus, the uplink system serial bus data exchange system based on serial bus which was obtained so that the output data
In the case of read / write data of upstream data format,
After that, an error flag is inserted, and the address data and command
Insert a data checker after the
Insert a data checker after read / write data,
Dress data, command data '' and `` write data
Data can be checked independently of each other
When the consistency of each data check is confirmed,
Start outputting response data to the serial bus
Address data and command data
Check is OK and the data check is performed in the write data part.
When an error occurs, the upstream data format
A data exchange method using a serial bus, characterized in that a response is made by turning on an internal error flag .