Communication Between the PAC and I/O

The M580 safety CPU and Copro together control all backplane exchanges, while the safety I/O respond to the commands of the CPU and Copro. Safety I/O modules can be installed in either a BMXXBP•••• X Bus rack or a BMEXBP•••• Ethernet rack.

Communications between the safety PAC and safety I/O modules in the local main rack are made via the backplane.

Communications between the safety PAC and safety I/O modules installed in an RIO drop are made through an adapter module installed on the RIO drop, either:

  • a BMECRA31210 adapter, for an Ethernet rack, or

  • a BMXCRA31210 adapter, for an X Bus rack.

NOTE: With CPU firmware 3.20 or later, the BM•CRA31210 adapter module needs a firmware 2.60 or later.
NOTE: A BMXCRA31200 adapter cannot be used to connect safety I/O modules to the M580 safety PAC.

Communications from the safety PAC and safety /O modules, both in the local main rack and in an RIO drop, are made via the black channel.

The way to synchronize the time settings of the CPU and the safety I/O modules is dependent to the CPU firmware version:

  • For PAC with CPU firmware 3.10 or earlier, the NTP service configuration is required.

    NOTE: If you are installing safety I/O modules on local rack (or in an extension of the local rack), it is not required to enable the NTP service.

  • For PAC with CPU firmware 3.20 or later, the safe time synchronization is based on an internal and "monotonic" time clock.

For more information refer to chapter Time Synchronization.

Optionally, you can use BMXNRP0200 or BMXNRP0201 fiber optic repeater modules to extend the physical link between the CPU and Copro in the local rack and the adapter in the RIO drop. Fiber optic repeater modules enhance RIO network noise immunity and increase cabling distance while maintaining the full dynamic range of the network and the safety integrity level.

The communication protocol between the safety I/O and PAC enables their exchanges. It permits both devices to check the accuracy of received data, detect corrupted data, and determine if the transmitting module becomes non-operational. Thus, a safety loop may include any non-interfering RIO adapters and backplane.

Supplying Power to the Safety I/O

The safety I/O is supplied 24 VDC and 3.3 VDC power over the backplane by the M580 safety power supply module. The safety power supply module monitors the power it provides so as not to exceed 36VDC.

Power for Non-Safety Functions:

5 VDC power provided by the backplane is applied by each safety I/O module to its non-safety functions.

External Power for Digital Safety I/O:

An external power supply, not greater than 60 VDC, is required for non-safety processes (sensor, actuator), and can be a protected extra-low voltage (SELV/PELV) overvoltage category II type power supply. The non-safety process power supply is supervised by the safety I/O module for overvoltage and undervoltage conditions.