Rockwell Automation AADvance Controller Configuration Guide - Manual (Page 67)

 
Document: 553633
ICSTT-RM405f-EN-P
Issue 07
4-27
Using the Controller as a Modbus Slave
The AADvance controller can operate as a Modbus slave, supporting up to ten
Modbus slaves on each 9110 processor module. This gives a capacity of thirty
Modbus slaves for a controller with three processor modules.
Note: As a Modbus slave device, the controller only transmits data upon a request
from a Modbus master, and does not communicate with other slaves.
Support for Modbus Slave Exceptions
When the AADvance controller operates as a Modbus slave, it can raise these
exception codes:
Code 01: Illegal Function
The function code received in the query is not an allowable action for the slave. If a
Poll Program Complete command was issued, this code indicates that no program
function preceded it.
Code 01 represents a function that the AADvance controller does not recognize or
does not support.
Code 02: Illegal Data Address
The data address received in the query is not an allowable address for the slave.
The AADvance controller raises code 02 when a request specifies an address outside
the 16-bit range 0 to 65,535. The exception occurs if the request specifies the address
implictly ('give me the 20 registers from address 65,530') or explicitly (give me the
register at address 65,536').
Code 03: Illegal Data Value\
A value contained in the query data field is not an allowable value for the slave.
The AADvance controller can raise code 03 only on boolean (coil) writes.
Code 04: Slave Device Failure
An unrecoverable error occurred while the slave was attempting to perform the
requested action.
Code 04 represents an internal error within the AADvance controller.
Code 06: Slave Device Busy
The slave is engaged in processing a long-duration program command. The master
should retransmit the message later when the slave is free.
The AADvance controller can be 'busy' and thus raise code 06 while it is waiting for
its application to download or to start. The controller can be report itself to be busy
for up to 30 seconds; after this period, the controller will cease to respond.