Chapter 4. CPU Operation168 PACSystems* RX7i, RX3i and RSTi-EP CPU Reference Manual GFK-2222AD4.10.1 I/O ConfigurationModule IdentificationIn addition to the catalog number, the programming software stores a Module ID for each configuredmodule in the hardware configuration that it delivers to the CPU. The CPU uses the Module ID todetermine how to communicate with a given module.When the hardware configuration is downloaded to the CPU (and during subsequent power-ups), theCPU compares the Module IDs stored by the programmer with the IDs of the modules physically presentin the system. If the Module IDs do not match, a System Configuration Mismatch fault will be generated.Because I/O modules of similar type may share the same Module ID, it is possible to download aconfiguration containing a module catalog number that does not match the module that is physicallypresent in the slot without generating a System Configuration Mismatch.Certain discrete modules with both reference memory inputs and reference memory outputs willexperience invalid I/O transfer if incorrect configuration is stored from a similar mixed I/O module. Nofault or error condition will be detected during configuration store and the module will be operational,although not in the manner described by configuration.For example, a configuration swap between the IC693MDL754 output module and IC693MDL660 inputmodule will not be detected as a configuration mismatch, but I/O data transfer between the module andthe CPU reference memory will be invalid. If the input module (MDL660) is sent the configuration of theoutput module (MDL754) with the following parameters:Reference Address: %Q601Module Status Reference: %I33Hold Last State EnableIt will receive inputs at the module status reference %I33 and the status of the module will be receivedat %Q601.If the output module is sent the configuration of the input module with the following parameters:Reference Address: %I601Input Filter: EnableDigital Filter Settings Reference: %I65It will output values at the digital filter settings reference %I65 and the status of the module will bereceived at %I601.
