Delta AH500 - Page 585

Chapter 6 Applied Instruction
6-417
word, and n should be within the range between 1 and 120.
6. The instruction can be used several times in the program, but one instruction is executed at a
time.
7. If the communication timeout occurs, SM104 and SM105 are ON. After the problem is solved,
users have to reset SM104 and SM105 to OFF. When using the instruction MODRW, the
timeout value cannot be 0, and the value should be set between 100 ~ 65535ms.
8. In the MODBUS ASCII mode, users only need to set up the data for transmission, the
instruction will add the head code (:), error checking code (LRC) and tail code (CRLF). The
data which is received is stored as the ASCII character in the internal register. The AH500
series PLC automatically converts the data into the hexadecimal value, and the conversion
result is stored in S.
9. In the MODBUS RTU mode, users only need to set up the data for transmission, the
instruction will add the checking code (CRC) and the data which is received is stored as the
ASCII character in the internal register. The AH500 series PLC automatically converts the data
into the hexadecimal value, and the conversion result is stored in S.
Communication protocol setup example:
1. Users can set up the PLC communication port in HWCONFIG or set values in the relative
spcial auxiliary relays to set up the communication. Please refer to ISPSoft manual for setups
in HWCONFIG. As for communication register setups (SM, SR), please refer to API1800 RS
instruction for more information.
2. The communication setup for this example is RS485 ASCII, 9600, 8, E, 1.
3. Communication port for data transmission is RS485 (SR215=1).
4. The transmission speed and format for the communicationport are 9600, 8, E, 1
(SR209=16#002D).
5. Set the number of times the command is resent (SR211=1).
6. Set the communication timeout to 3000ms (SR210=3000).
7. Set the communication mode to ASCII mode (SM210=OFF).
8. Enable the communication protocol (SM209=ON).
For users who set up the communication port in ISPSoft－＞HWCONFIG－＞COM Port, this step
can be ignored.