Month: September 2025

Positive or Negative Inputs

Inputs for this module can be either positive or negative inputs (all 16 inputs must be the same

type). Both types of signal produce a logic 1 (true) when the switch is closed. Selection of

positive or negative operation is made by the manner in which the external power supply is

connected to the inputs and to the I/O Terminal Block.

Positive inputs receive current from input devices and supply current to the common or negative

power bus. Input devices are connected between the positive power bus and the input terminals.

Negative inputs provide current to input devices and accept current from the common or

positive power bus. Input devices are connected between the negative power bus and the input

terminal.

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.

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.

Positive or Negative Inputs

Inputs for this module can be either positive or negative inputs (all 16 inputs must be the same

type). Both types of signal produce a logic 1 (true) when the switch is closed. Selection of

positive or negative operation is made by the manner in which the external power supply is

connected to the inputs and to the I/O Terminal Block.

Positive inputs receive current from input devices and supply current to the common or negative

power bus. Input devices are connected between the positive power bus and the input terminals.

Negative inputs provide current to input devices and accept current from the common or

positive power bus. Input devices are connected between the negative power bus and the input

terminal.

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.

The 24 VDC Positive/Negative Fast Input Module (IC670MDL644) provides a single group of

16 discrete inputs, which may be driven by positive or negative logic.

Power Sources

The module receives power from the Bus Interface Unit 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.

Product Description  

The RTD Input Modules allow RTD temperature sensors to be directly connected to the PLC 

without external signal processing (transducers, transmitters, etc.).  All analog and digital processing of 

the RTD signal is performed on the module, and temperature values in 0.5°C or 0.5°F increments 

(RTD600) or 0.125°C, 0.1°C or 0.1°F (RTD601) increments are written to the 90-30 %AI input table.  All 

modules feature six channels, and support PT-90 (MIL-7990); PT-100E, PT-100C, and PT-100Z; Ni-120, 

Cu-10, Cu-50, Cu-53, Cu-100, Pt-1000, TD5R and Linear Resistance. 

ABOUT PROGRAMMING EXAMPLES

Any example programs and program segments in this manual or provided on accompanying diskettes are

included solely for illustrative purposes.  Due to the many variables and requirements associated with any

particular installation, Horner APG cannot assume responsibility or liability for actual use based on the

examples and diagrams.  It is the sole responsibility of the system designer utilizing the Resistance

Temperature Device Input module to appropriately design the end system, to appropriately integrate the

Resistance Temperature Device Input module and to make safety provisions for the end equipment as is

usual and customary in industrial applications as defined in any codes or standards which apply.