Yudian AIBUS Communication Protocol Description (V7.0)

AIBUS is a communication protocol developed by Xiamen Yudian Automation Technology Co., Ltd. for AI series display control instruments. It can realize powerful functions with simple instructions and provide faster rate than other common protocols (such as MODBUS) (same baud rate) 3-10 times faster), suitable for building larger scale systems.


AIBUS is a communication protocol developed by Xiamen Yudian Automation Technology Co., Ltd. for AI series display control instruments. It can realize powerful functions with simple instructions and provide faster rate than other common protocols (such as MODBUS) (same baud rate) 3-10 times faster), suitable for building larger scale systems. AIBUS adopts 16-bit summation correction code, reliable communication, supports 4800, 9600, 19200 and other baud rates. At 19200 baud rate, the upper computer accesses an average of AI-7/8 series high-performance instruments. The time is only 20mS, and the average time to access the AI-5 series meters is 50mS. The instrument allows up to 80 instruments to be connected to one RS485 communication interface (to ensure reliable communication, an RS485 repeater is required when the number of instruments is greater than 60). AI series instruments can use PC, touch screen and PLC as the host computer. The software resources are abundant and the development speed is extremely fast. The PC software of the base and PC widely adopts WINDOWS as the operating environment, which is not only intuitive and convenient to operate, but also powerful. The application of the latest industrial flat panel touch screen PC brings a new interface to industrial automation. This makes the AIDCS system much cheaper than the traditional DCS system, and the performance and reliability also have superior potential than the traditional DCS system. The V7.X version of the AI-7/8 series of instruments allows continuous writing of parameters, writing of setpoints or outputs. Value, you can use the host computer to make the instrument into a complex adjustment system.

First, the interface specifications

The AI ​​series instruments use an asynchronous serial communication interface, and the interface level complies with the provisions of the RS232C or RS485 standards. The data format is 1 start bit, 8 bits of data, no parity, 1 or 2 stop bits. The baud rate of the communication transmission data can be adjusted to 4800~19200 bit/S, usually 9600 bit/S. When the number of instruments connected to a single communication port is more than 40 or a faster refresh rate is required, it is recommended to use 19200bit/S. When the distance is long or the communication is unreliable and often interrupted, 4800bit/S is optional. The AI ​​instrument adopts multi-machine communication protocol, and adopts RS485 communication interface, which can connect 1~80 instruments at the same time to one communication interface.

RS485 communication interface communication distance is more than 1KM (some practical applications have reached 3-4KM), only two lines can make multiple AI instruments communicate with the computer, better than RS232 communication interface. In order to use the ordinary personal computer PC as the host computer, RS232/RS485 or USB/RS485 type communication interface converter can be used to convert the RS232 communication port or USB port on the computer into the RS485 communication port. For this purpose, Yudian has developed a new RS232/RS485 and USB/RS485 converter, which has the advantages of small size, no need to initialize and can adapt to any software, no external power supply, and certain anti-lightning capability.

According to the RS485 interface, the RS485 communication interface can connect up to 32 instruments or computers on one communication line. When you need to connect more instruments, you need a repeater, or you can choose the communication interface of the chip such as 75LBC184 or MAX487. The current AI instrument communication interface module usually adopts 75LBC184. This chip has certain lightning protection and anti-static functions, and can connect about 60 instruments without repeaters.

The RS232 and RS485 communication interfaces of the AI ​​instrument use optical isolation technology to isolate the communication interface from other parts of the instrument. When one of the instruments on the communication line is damaged or faulty, it will not affect other instruments. Similarly, when the communication part of the instrument is damaged or the host fails, the instrument can still measure and control normally, and the instrument can be operated through the instrument keyboard, and the work reliability is high. The correctness of the 16-bit check code is 30,000 times that of simple parity, which basically guarantees data reliability. And when other companies on the same network also use the master-slave communication products, such as PLC, inverter, etc., in most cases, the AI ​​series instruments will not be interfered by other company's product communication, and there will be no confusion or communication failure. problem. However, the AI ​​instrument protocol does not guarantee the normal operation of other company products, so unless it is absolutely necessary, the AI ​​instrument should not be mixed with other products on an RS485 communication bus, but different buses should be used separately.

Second, the communication instructions

The AI ​​meter uses a hexadecimal data format to represent various instruction codes and data. The AI ​​instrument software communication instruction is optimized. There are only two standard communication commands. One is the read command and the other is the write command. The two commands make the PC software easy to write, but can operate the instrument 100% completely. The read and write instructions are as follows:

Read: Address code +52H (82) + parameter code to be read +0+0 + check code

Write: Address code +43H (67) + parameter code to be written + write number low byte + write number high byte + check code

Address code: In order to connect multiple AI instruments on one communication interface, each AI instrument needs to be programmed with a different communication address. The valid address is 0~80 (some models are 0~100), so up to 81 AI instruments can be connected to one communication line. The communication address of the instrument is determined by the parameter Addr. The internal number of the instrument uses two repeated values ​​of 128~208 (hexadecimal 80H~D0H) to indicate the address code. Since the number greater than 128 is less used (such as the ASC mode protocol usually only uses 0-127). The number), thus reducing the possibility of conflicts due to data and address duplication.

The AI ​​instrument communication protocol stipulates that the address code is two identical bytes and the value is (meter address +80H). For example, if the instrument parameter Addr=10 (hexadecimal number is 0AH, 0A+80H=8AH), the address code of the instrument is: 8AH 8AH

Parameter code: The parameter of the meter is represented by the parameter code of an 8-bit binary number (one byte, written as a hexadecimal number). It indicates the name of the parameter to be read/written in the instruction.

Check code: The check code adopts 16-bit sum check mode. The check code calculation method of read command is:

The code to read the parameter ×256+82+ADDR

The check code calculation method of the write command is the remainder calculated by the 16-bit binary addition of the following formula (the overflow part is not processed):

The parameter code to be written ×256+67+ parameter value to be written +ADDR

In the formula, ADDR is the value of the instrument address parameter, and the range is 0~80 (be careful not to add 80H). The check code is the remainder obtained by adding the binary 16-bit integer to the above formula, and the remainder is 2 bytes, with the low byte first and the high byte after. The parameter values ​​to be written are represented by 16-bit binary integers.

Return data: Whether reading or writing, the meter returns the following 10 bytes of data:

Measured value PV+ given value SV+ output value MV and alarm status + read/write parameter value + check code

The PV, SV and read parameter values ​​each occupy 2 bytes, representing a 16-bit binary signed complement integer. The lower byte is first, the high byte is after, and the integer cannot represent the decimal point. The user is required to be in the upper computer. Processing; MV occupies one byte, in 8-bit signed binary number format, the value range is -110~+110, the status bit occupies one byte, and the check code occupies 2 bytes, a total of 10 bytes.



The meanings of the data returned by different models are as follows:

Instrument model

Regulator

thermostat

AI-708M inspection instrument

AI-708H/808H

Flow channel

AI-808H

Temperature/pressure channel

AI-301M frequency regulator / IO module

PV

Measured value PV

Measurements

Instantaneous flow measurement



Temperature measurement in 0.1 ° C

Measured value PV

SV

Current given value SV

Channel number

(1-6)

Cumulative flow low

Or batch control of measured values

Pressure measurement in 0.001 MPa

Current given value SV

MV

Output value MV

Status byte B

Status byte B

Cumulative flow high

Or batch control of a given value

Pre-compensation flow or frequency value in 0.1 Hz

Adjust the output value MV

Status byte

Status byte A

Status byte A

Status byte A

Parameter value

Indicates the value of the parameter to read or write



Return check code: PV+SV+ (alarm status *256+MV) + parameter value + ADDR The remainder obtained by adding the integers. When calculating the check code, every two 8-bit bytes form a 16-bit binary integer for addition, the overflow number is ignored, and the remainder is used as the check code.

The status byte A indicates the status of the instrument part, and its meaning is as follows (bit 7 is fixed to 0):



Regulator and single display (V7.0)

AI-702M/704M/706M

Regulator, thermostat and single display (V7.5)

Bit 0

Upper limit alarm (HIAL)

Upper limit alarm (HIAL)

HIAL

Bit 1

Lower limit alarm (LoAL)

Lower limit alarm (LoAL)

LoAL

Bit 2

Positive deviation alarm (dHAL)

0

HdAL

Bit 3

Negative deviation alarm (dLAL)

0

LdAL

Bit 4

Enter overrange alarm (orAL)

Overrange alarm (orAL)

orAL

Bit 5

AL1 state, 0 is action

0

Alternate (0)

Bit 6

AL2 state, 0 is action

0

0 means MV is the output value, 1 is the status word B.



The patrol instrument has a status byte B. For V7.5 version or higher regulators, temperature controllers, and single display meters, the MV can alternately represent the MV value and status byte B (determined by bit 6 of status byte A). Bits 0~6 of status byte B indicate the input states of OP1, OP2, AL1, AL2, AU1, AU2, and MIO, respectively. 0 indicates no turn-on or no output, 1 indicates that the external switch is on or has output, OUTP Or the corresponding bit is fixed to 0 when AUX is making adjustment output. The function can be used as the output or output of the switch of the host computer. The alarm port that is not used by the ALP parameter setting can be used as the I/O port. The switch can be realized by modifying the NONC (normally open/normally closed) parameter. The output of the quantity, when used as a digital input, should set the nonc corresponding bit to normally open. If the read signal is 1, it means that the external switch is closed or has a signal input.



Parameter code table for AI instrument read/write:

Table I

Parameter code

Regulator

Inspection instrument

10 hex

Hex

AI-518/708/808/518P/708P/808P

AI-519/719/719P

AI-501/701

AI-702M/704M/706M

0

00H

SV reference / SteP block

SV reference / SteP block

(air)

(air)

1

01H

HIAL upper limit alarm

HIAL upper limit alarm

HIAL upper limit alarm

HIAL upper limit alarm

2

02H

LoAL lower limit alarm

LoAL lower limit alarm

LoAL lower limit alarm

LoAL lower limit alarm

3

03H

dHAL positive deviation alarm

HdAL deviation upper limit alarm

HdAL second upper limit alarm

(air)

4

04H

dLAL negative deviation alarm

LdAL deviation lower limit alarm

LdAL second lower limit alarm

(air)

5

05H

dF hysteresis

CHYS control hysteresis

AHYS alarm backlash

dF hysteresis

6

06H

Ctrl control mode

Ctrl control mode

(air)

(air)

7

07H

M5 keeps parameters

P proportional band

(air)

(air)

8

08H

P rate parameter

I integration time

(air)

(air)

9

09H

t lag time

d differential time

(air)

(air)

10

0AH

CtI control cycle

CtI control cycle

(air)

Cn measurement path

11

0BH

Sn input specification

InP input specifications

InP input specifications

Sn input specifications

12

0CH

dIP decimal point position

dPt decimal point position

dPt decimal point position

dIP decimal point position

13

0DH

dIL input lower limit display value

SCL signal scale lower limit

SCL signal scale lower limit

dIL input signal scale lower limit

14

0EH

dIH input upper limit display value

SCH signal scale upper limit

SCH signal scale upper limit

dIH input signal scale upper limit

15

0FH

ALP alarm output definition

AOP alarm output definition

AOP alarm output definition

ALP alarm input definition

16

10H

Sc input translation correction

Scb input translation correction

Scb input translation correction

Sc input translation correction

17

11H

OP1 output mode

OPt main output type

OPt main output type

OPn transmission output channel number

18

12H

oPL output lower limit

OPL output lower limit

(air)

oPL transmission output current lower limit

19

13H

oPH output limit

OPH output limit

(air)

oPH transmission output current limit

20

14H

CF function selection

AF advanced function code

(air)

AF advanced function code

twenty one

15H

Meter signature/program control word (Run: 0 Pause: 4 Stop: 12)

Meter signature/program control word (Run: 0 Pause: 4 Stop: 12)

Instrument signature (same value as SV, and can be modified)

Instrument signature

twenty two

16H

Meter address (read/write)

Meter address (read/write)

Meter address (read/write)

Meter address (read/write)

twenty three

17H

dL digital filtering

FILt input digital filtering

FILt input digital filtering

dL digital filtering

twenty four

18H

Run run parameter

AM automatic / manual control selection

(air)

Nonc normally open / normally closed selection

25

19H

Loc parameter blocking

Loc parameter blocking

Loc parameter blocking

Loc parameter blocking

26

1AH

C01

(Set the MV value when AI-808 is written)

C01 (set MV value when AI-519/719 is written)





27

1BH

T01

T01





28

1CH

C02

C02





29

1DH

T02

T02





30

1EH

C03

C03





31

1FH

T03

T03





32

20H

C04

C04





33

21H
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