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171CCC780x0 M1 Processor Port 2 Modbus Master Communication Problem

Release Notice

The purpose of this resolution is to inform Momentum Processor users that a problem exists with port 2 of a 171CCC780x0 M1 when used as a Modbus Master port for Modbus RS485 communications. This problem only affects port 2 communications when configured as a Modbus Master. This does not affect port 2 Modbus slave communications or functionality.

Goals and Symptoms

A Response Timeout Error (116) is displayed in the XMIT or XXMIT Function Block when using Port 2 as a Modbus Master communicating to a slave device. Although a query is sent by the M1 and the slave responds properly to the query, the data is not received by the M1.

Facts and Changes

The M1 processors affected are: 171CCS78000, 171CCC78010, and 171CCC78010K.

Causes and Fixes

The component exhibiting the problem described is an Innovasic PTQ1001-01 (refer to the highlighted component in the diagram below) and is no longer used in manufacturing. All AMD or Innovasic PTQ1001-03 components used in this location work properly and do not exhibit the problem. The component can be viewed without removal of the PC board from the plastic case.

  • Although new PV and RL numbers used to identify those M1 processors with the updated component will not be assigned until April 2007, M1 171CCC780x0 processors are already being manufactured with the Innovasic PTQ1001-03. M1 processors with serial numbers greater than 210640xxxxx have the Innovasic PTQ1001-03 and are good.
  • If Modbus Master communication problems from port 2 remain, even with the proper AMD or Innovasic PTQ1001-03 processors installed, check the cabling or the XMIT/XXMIT Function Block configuration.
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