Non-blocking Condition Diagnostics

Introduction

The system encounters 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 operating state.

This topic describes some of the system bits and words you can use to detect the state of the safety system and its component modules.

NOTE: The available system bits and words do not include all information relating to the state of safety modules. Schneider Electric recommends that you use the DDDT structure of the safety CPU and safety IO modules to determine the state of the M580 safety system.

For information about the M580 safety CPU DDDT, refer to the topic Standalone DDT Data Structure for M580 CPUs in the Modicon M580 Hardware Reference Manual.

For information about the M580 safety I/O module DDDTs, refer to the following topics:

BMXSAI0410 Data Structure for the safety analog input module.
BMXSDI1602 Data Structure for the safety digital input module.
BMXSDO0802 Data Structure for the safety digital output module.
BMXSRA0405 Data Structure for the safety digital relay output module.

NOTE: You can also perform more advanced diagnostics of Ethernet devices by means of explicit messaging. To accomplish this, use either:

the READ_VAR function block for Modbus TCP devices.
the DATA_EXCH function block, specifying the CIP protocol in the ADDM block, for EtherNet/IP devices.

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
I/O module LED pattern: steady ON
system bits (type of detected error):
- %S10 set to 0: global I/O error detected on one of the modules on the local or remote Ethernet or X Bus rack
- %S16 set to 0: I/O error detected in the task in progress on an X Bus rack
- %S40...%S47 set to 0: I/O error detected on an X Bus rack at address 0 to 7
- %S117 set to 0: RIO error detected on a remote X Bus rack
- %S119 set to 0: I/O error detected on a local X Bus rack
  
  NOTE: These bits (%S10, %S16, %S40...%S47, %S117, and %S119) report many – but not all – of the possible detected errors relating to safety I/O modules.
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.
  
  (Refer to the topic System Bits for Safe Task Execution for more information.)
  
  When %S18 is set to 1, %SW17 contains a description of the causal event.
- %S20 set to 1: index overrun.
NOTE: If the configurable system bit %S78 is set in the program, the SAFE task enters the HALT state when system bit %S18 set to 1.
system word – nature of the error detected:
- %SW125 (always updated)