Power Sources

The module receives power from the Bus Interface Unit for its own operation. An external 48

VDC 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, capacitors, and zener diodes establishes input thresholds and provides

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

components. An oscillator and switch form a sampling circuit that is transparent to the

controller and the LEDs that indicate the state of the inputs. 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-serial converters change input data from the data buffer into the serial format

needed by the Bus Interface Unit.