ABB ECA06 - A.2 Protocol Description; Modbus Communication

A.2 Protocol Description Appendix A: Communication
282 493-0736-11 (6-2)
Recommended max number of units per master system is 10 slaves. This is due
to the response time when cyclically requesting information from all slaves.
A.2 Protocol Description
Modbus Communication
Function Codes
ECA can only work as a MODBUS slave and supports the following MODBUS
function codes.
Message codes [01] and [02] are treated as a read operation in the ”I/O RAM
Map” in the ECA.
Message codes [03] and [04] are treated as a read operation in the ”Register Map”
in the ECA.
Message code [05] is a write operation in the ”I/O RAM Map” (write single bit).
Message code [06] is a write operation in the ”Register Map” (write single
register).
Response Codes
ECA supports the following response codes:
Code Designation Function
01 Read Coil Status Read binary values
02 Read Input Status Read binary values
03 Read Holding Registers Read registers (16 bits Integer)
04 Read Input Registers Read registers (16 bits Integer)
05 Force Single Coil Write/Set a single register value (1 bit)
06 Preset Single Register Write/Set a single register value (16 bits
Integer)
Code Name
01 Illegal function