A-B 1746-OB8 module Rockwell SLC 8 digital output control

Response to Slot Disabling

By writing to the status file in your modular SLC processor you can disable any chassis slot.

See your SLC programming manual for the slot disable/enable procedure.

Input response

When the slot for this module is disabled, the module continues to

update its inputs. However, the SLC processor does not read from a

module whose slot is disabled. Therefore, inputs appearing in the

processor image table remain in their last state, and the module’s

updated inputs are not read. When the processor re–enables the

module slot, the current state of module inputs are read by the

controller during the subsequent scan.

Output response

When the slot for this module is disabled, configuration words in the

SLC processor’s output image table are held in their last state and not

transferred to the module. When the slot is re–enabled, output image

table words are transferred to the module during the subsequent scan.

Installing and Wiring

This document gives you information about:

• avoiding electrostatic damage

• compliance with European Union directive

• determining the module’s chassis power requirement

• planning for sufficient enclosure depth

• choosing a module slot in a local I/O chassis

• installing the module

• wiring the module

Installing the Module

Follow this procedure:

ATTENTION

!

Never install, remove, or wire modules with power applied to the chassis or devices wired to the module.

1. Align the circuit board of the thermocouple module with the card guides located at the top and bottom of the chassis.

2. Slide the module into the chassis until both top and bottom retaining clips are secured. 

Apply firm even pressure on the module to attach it to its backplane connector.

Never force the module into the slot.

3. Cover unused slots with the card slot filler, catalog number 1746–N2.

4. To remove, press the releases at the top and bottom of the module, and slide the module out of the chassis slot.

Current CV

Your ladder logic should read the numeric value (current CV), scale it,

and send it to an analog output module to generate the control signal

to an analog temperature control actuator. If using the sample

program look for current CVs in N10:208–211 for loops 1–4. 

TPO

The module returns the heat TPO (bit 6) and cool TPO (bit 7) in input

image table words 8–11 for loops 1–4. The sample program sends

TPO signals to a digital output module to generate the control signal

to a digital temperature control actuator.

Module Addressing

When you enter the module ID in processor configuration (off-line),

the processor automatically reserves the required number of I/O

image table words. In the figure below, that section of the I/O image

table is designated by “slot e”. Its location in the I/O image table is

determined by the module’s slot location “e” in the I/O chassis. Slot

location “e” is a required addressing unit when referring to the

module in ladder logic. For the sample program’s data table layout

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