Introduction

The system enters a non-blocking condition when it detects an input/output error on the backplane bus (X Bus or Ethernet) or through execution of an instruction, which can be processed by the user program and does not modify the CPU status.

Conditions Linked to I/O Diagnostics

A non-blocking condition linked to the I/O is diagnosed with the following indications:

• CPU I/O LED pattern: steady ON

• module I/O LED pattern: steady ON

• system bits (type of error):

  • %S10 set to 0: I/O error detected on one of the modules on the rack (channel power supply detected error, or broken channel, or module not compliant with the configuration, or inoperative module, or module power supply detected error)

  • %S16 set to 0: I/O error detected in the task in progress

  • %S40–%S47 set to 0: I/O error detected on rack address 0 to 7

• system bits and words combined with the channel having an error detected (I/O channel number and type of detected error) or I/O module Device DDT information (for modules configured in Device DDT addressing mode):

  • bit %Ir.m.c.ERR set to 1: channel error detected (implicit exchanges)

  • word %MWr.m.c.2: the word value indicates the type of error detected on the specified channel and depends on the I/O module (implicit exchanges)

Conditions Linked to Execution of the Program Diagnostics

A non-blocking condition linked to execution of the program is diagnosed with the following system bits and words:

• system bits (type of error detected):

  • %S15 set to 1: character string manipulation error detected

  • %S18 set to 1: capacity overrun, error detected on a floating point, or division by 0

  • %S20 set to 1: index overrun

• system word (nature of the error detected):

  • %SW125 (always updated)

There are 2 ways to force a CPU to stop when non-blocking errors linked to the execution of the program are detected:

• Use the diagnostic program function accessible through Control Expert programming software.

• set the system bit %S78 (HALTIFERROR) to 1.