Watlow CLS200, MLS300 and CAS200 - Manual (Page 32)

26 Communications Specification
Chapter 2: Modbus-RTU Protocol
This process is repeated until eight shifts have been performed. After the
last shift, the next 8-bit byte is exclusive ORed with the register’s
current value, and the process repeats for eight more shifts as described
above. The final contents of the register, after all the bytes of the
message have been applied, is the CRC value.
Function Codes
The listing below shows the function codes supported by the CLS
controllers. Codes are listed in decimal.
x01 Read Coil Status
• Reads the On/Off status of discrete outputs (registers 00001 to
09999, the coils) in the slave. Broadcast is not supported.
x02 Read Input Status
• Reads the On/Off status of discrete inputs (registers 10001 to 19999)
in the slave. Broadcast is not supported.
x03 Read Holding Registers
• Reads the binary contents of holding registers (registers 40001 to
49999) in the slave. Broadcast is not supported.
x04 Read Input Registers
• Reads the binary contents of input registers (registers 30001 to
39999) in the slave. Broadcast is not supported.
x05 Force Single Coil
• Forces a single coil (registers 00001 to 09999, the coils) to either On
or Off. When broadcast, the function forces the same coil reference
in all attached slaves.
Code
in Hex
Name
01 Read Coil Status
02 Read Input Status
03 Read Holding Registers
04 Read Input Registers
05 Force Single Coil
06 Preset Single Register
08 Diagnostics
0F Force Multiple Coils
10 Preset Multiple Registers