Power Sources

The module receives power from the Field Processor to run its own 5–volt logic. An external

24VDC supply is needed to power the input devices.

LEDs

Individual LEDs (logic side), visible through the transparent portion of the module top,

indicate the on/off status of each input. The PWR LED is on when field and backplane power

are present.

Host Interface

Intelligent processing for this module is performed by the Bus Interface Unit or elsewhere in

the system. This includes configuring features such as input defaults and fault reporting. The

module has 16 bits (two bytes) of discrete input data. A Bus Interface Unit is required to

provide this input data to the host and/or local processor.

Module Operation

A network of resistors and capacitors establishes input thresholds and provides input filtering.

Optoisolators provide isolation between the field inputs and the module’s logic components.

Data from all 16 inputs is placed into a data buffer. The module’s circuit LEDs show the

current states of the 16 inputs in this data buffer.

Parallel–to–seri al converters change input data from the data buffer into the serial format

needed by the Bus Interface Unit.

After checking the Board ID and verifying that the module is receiving appropriate logic power

from the Bus Interface Unit (which is reflected by the state of the module’s Power LED), the Bus

Interface Module then reads the filtered, converted input data.