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MAN0995_Iss 1_01/16
Touchpoint Plus
Pt. No. 3011M5027_1
16
Modbus Installation Guide
4.8 Exception Responses
The Modbus exception response is detailed in the
Modicon Modbus Protocol Reference Guide
. Any one of the following
exception responses may be returned by the Touchpoint Pro Modbus interface:
Exception
Description
01 ILLEGAL FUNCTION
Only Modbus functions 02, 03, 04 and 06 are supported. This response is returned if
any other requests are received.
02 ILLEGAL DATA ADDRESS The register addresses supported by each function are listed in this chapter. Any
attempt to access a register outside of these ranges will result in this error.
03 ILLEGAL DATA VALUE
This exception is returned if the request has the incorrect length, or if the maximum
number of registers is exceeded. The maximum number of registers that can be
requested by function 02 is 512, function 04 is 64, and function 03 is 36 for the Query
poll block or 6 for the Command poll block.
06 SLAVE DEVICE BUSY
Applies to function 06 only. Once a poll or command block’s active register has been
set, its contents must not be changed until the main program has carried out the
request. This exception is returned if any attempt is made to change an active poll or
command block.
Table 16.
Modbus Exception Responses
