Month: July 2025

SLC Servo Module Overview

The SLC Servo Module (catalog number 1746-HSRV) is compatible 

with the SLC 500 family and only used with SLC 5/03™ FRN 5.0, SLC 

5/04™, or SLC 5/05™ SLC Servo Modules. The SLC Servo Module is 

programmed for incremental, absolute or speed moves, depending on 

the application.

IMPORTANT

Place the SLC Servo Module as close to the SLC processor as possible

Command Mode Operation

Motor operations are performed in command mode. To operate in this 

mode, set the mode flag (bit 15 in output word 0) to 0. In the 

command mode, the SLC processor issues commands and activates 

the following operations or moves:

• Absolute moves 

• Incremental moves

• Speed moves

• Monitor moves

• Hold moves

• Unhold moves

• Blend moves

• Emergency stop operations

• Homing operations

• Preset operations

• Clear faults

• Alternate home moves

Short-Circuit/Overload Current Diagnostics

If a short-circuit or overload current condition occurs on an output channel:

1. The FLT LED flashes, provided that power is applied to the module. 5V dc via 

backplane and load power via an external supply is required.

2. Fuse status bit (FB1) is set (1) when the fuse is tripped. The module tries to 

reset the outputs at intervals of 500 ms. During each retry, the fuse status bit is 

reset (0). After the overload condition is corrected, the fuse status bit resets (0) 

automatically.

When FB1 is set, outputs 0 through 4 will not function.

3. All output channels will be turned off in the case of a short-circuit or overload condition.

Recovery from Channel Shutdown

1. Remove the SLC 500 system power and correct the conditions causing the 

short-circuit or overload current condition.

2. Restore the SLC 500 system power. The module automatically resets and 

resumes control of the output channel and associated load.

Auto Reset Operation

IMPORTANT

1746-HSCE2 outputs perform auto-reset under overload 

conditions. When an output channel overload occurs as 

described above, all channels turn off within milliseconds 

after the thermal cut-out temperature has been reached. While 

the overcurrent condition is present, the module tries resetting 

the outputs at intervals of 500 ms. If the fuse cools below the 

thermal cut-out temperature, all outputs will auto-reset and 

resume control of their external loads as directed by the 

module until the thermal cut-out temperature is again reached.

Removing power from an overloaded output channel would 

also allow the fuse to cool below the thermal cut-out 

temperature, allowing auto-reset to occur when power is 

restored. The output channel then operates as directed by the 

module until the thermal cut-out temperature is again reached.

To avoid auto-reset of output channels under overload 

conditions, monitor the fuse blown status bit (FB1) in the 

module’s status file and latch the output off when an 

overcurrent condition occurs. An external mechanical fuse 

can also be used to open an output circuit when it is overloaded.

Considerations for Reducing Noise

In high noise environments, the 1746-HSCE2 inputs may accept “false” pulses, 

particularly when using low frequency input signals with slowly sloping pulse 

edges. To minimize the effects of high frequency noise on low frequency signals, 

the user can do the following:

• Identify and remove noise sources.

• Route 1746-HSCE2 input cabling away from noise sources.

• Install low pass filters on input signals. Filter values are dependent on the 

application and can be determined empirically.

• Use devices which output differential signals, like differential encoders, to 

minimize the possibility that a noise source will cause a false input.

Electronic Protection

The electronic protection of the 1746-HSCE2 has been designed to provide 

protection for the module from short-circuit and overload current conditions. The 

protection is based on a thermal cut-out principle. In the event of a short circuit or 

overload current condition on an output channel, all channels turn off within 

milliseconds after the thermal cut-out temperature has been reached.

Installing the Module

1. Make sure your SLC power supply has adequate reserve current capacity.

The  module requires 250 mA at +5V dc. 

2. Align the full-sized circuit board with the chassis card guide as shown below.

The first slot of the first chassis is reserved for the processor.

3. Slide the module into the chassis until the top and bottom latches catch. 

To  remove the module, press the release clips at the top and bottom of the module  and slide it out. 

4. Cover all unused card slots with the Card Slot Filler, catalog number 1746-N2.

Important Wiring Considerations

Use the following guidelines when planning the system wiring for the module:

• Install the SLC 500 system in a NEMA-rated enclosure.

• Disconnect power to the SLC processor and the module before wiring.

• Make sure the system is properly grounded.

• Group this module and low-voltage DC modules away from AC I/O or 

high-voltage DC modules.

• Shielded cable is required for high-speed input signals A, B, and Z. Use 

individually shielded, twisted pair cable lengths up to 300 m (1000 ft.).

• Shields should be grounded only at one end. Ground the shield wire outside 

the module at the chassis mounting screw. Connect the shield at the encoder 

end only if the housing is isolated from the motor and ground.

• If you have a junction in the cable, treat the shields as a conductor at all 

junctions. Do not ground them to the junction box.

Install the Module 

Installation procedures for this module are the same as for any other discrete I/O or  specialty module.

ATTENTION

Disconnect power before attempting to install, remove, or wire  the module. 

Make sure your SLC power supply has adequate reserve current  capacity. The module requires 320 mA at 5V dc.1. Align the full-size circuit board with the chassis card guide. 

The first slot of the first chassis is reserved for the CPU.

2. Slide the module into the chassis until the top and bottom latches are latched. 

Make sure the removable terminal wiring block is attached to the module 

and all wires are connected to the terminal block.

3. Insert the cable tie in the slots and secure the cable.

4. Cover all unused slots with the Card Slot Filler, Catalog Number 1746-N2.

Important Wiring Considerations

Use the following guidelines when planning the system wiring for the module:

• Install the SLC 500 system in a NEMA-rated enclosure.

• Disconnect power to the SLC processor and the module before wiring.

• Make sure the SLC 500 system is properly grounded. 

• Group this module and low-voltage DC modules away from AC I/O or 

high-voltage DC modules. 

• Shielded cable is required for high-speed input signals A, B, and Z. We 

recommend Belden 9503 or equivalent for lengths up to 305 m (1000 ft).

• When the LS input is driven by an electromechanical device, route the 

wiring away from other inputs. In addition, JW1 should be set for the 10 ms filter. 

• When the LS input is driven by a solid-state device, use a shielded cable. 

You do not have to route the cable away from other inputs. 

• Shields should be grounded only at the end of the signal source end of the 

cable. Ground the shield to the case of the signal source, so energy coupled 

to the shield will not be delivered to signal source’s electronics.

In addition, an Accumulated Counter, the module provides a Rate Counter to 

determine Rate Measurement by indicating the pulse input frequency in Hz. (See 

the block diagram on page 6.) The Rate Measurement is determined by 

accumulating input pulses over a fixed period of time. You set the Rate Period to 

best match your application requirements.

Background Rate calculation is provided in Sequencer and Range Modes. This 

operation accepts input rates up to 32,767 Hz. The dynamically configurable Rate 

Period ranges from 10 ms to 2.55 seconds. 

The module’s four current sink (open collector) outputs can be controlled in the 

user program or the module.

Control of the counter reset is configured through user-set parameters. The counter 

can be reset from any combination of the Z input, Limit Switch input, or Soft Reset control bits.

Module operation is determined by selections made in the Setup and Control Word 

(M0:e.1). Setting the Function Control bit to 1 triggers the module to start the 

proper pulse counter, rate measurement, and output control functions. Many 

parameters are dynamic and can be changed without disrupting counter operation. 

The module’s block diagram is shown on page 6. Inputs from the terminal block 

enter the diagram at the left, outputs to the terminal block exit at the right. M0 and 

Output file parameters from the SLC enter the logic blocks from the top. Input file 

data to the SLC exit the logic blocks from the bottom.

High-Speed Counter Module Overview

The High-Speed Counter Module, Catalog Number 1746-HSCE is an SLC 500 family 

compatible device except with the 1747-ASB Remote I/O Adapter Module. It can be 

used with SLC™ 5/02 (and above) processors.

The module’s bidirectional counting ability allows it to detect movement in either 

direction. In addition, x2 and x4 counting modes are provided to fully use the 

capabilities of high-resolution quadrature encoders.

High-speed inputs from quadrature encoders and various high-speed switches are 

supported. Accepting input pulse frequencies of up to 50k Hz allows precise 

control of fast motions.

Two dip switches (SW1 and SW2) and one jumper (JW1) are located on the side of  the module. 

• SW1 selects the type of input (single ended or differential). 

• SW2 selects the output voltage range (4.5 to 10V dc or 10 to 30V dc). 

• JW1 selects the filtering rate (300 µs or 10 ms) used to debounce the limit  switch input.

Install the Module 

Installation procedures for this module are the same as for any other discrete I/O or  specialty module.

Low Voltage Directive

This product is tested to meet Council Directive 73/23/EEC

Low Voltage, by applying the safety requirements of EN 61131–2

Programmable Controllers, Part 2 – Equipment Requirements and Tests.

For specific information required by EN 61131-2, see the appropriate

sections in this publication, as well as the following Allen-Bradley publications:

Industrial Automation Wiring and Grounding Guidelines 

(for noise immunity), publication 1770-4.1

Automation Systems Catalog, publication B111

Wiring the Module

Installing the Ferrite Collar

For immunity to electrical noise with this CE-marked module, insert

ferrite collar (Fair-Rite Inc. part number 0443164151) around the input

cables immediately beneath the module in the I/O chassis. 

Do this as follows:

1. Bundle the cables at the module end.

2. Fold the collar so that it encircles the cables.

3. Press the plastic housing until the collar snaps together.

4. Check that the collar is fully latched.

5. If the collar slides on the cables, use a cable tie to secure it.

To the Installer

This publication states compliance with directives required for using

analog I/O modules with the CE mark within the European Union or

EEA regions. It also provides instructions for inserting a ferrite collar

on the module’s input cable(s) for compliant immunity to electrical

noise. Use these instructions as a supplement to the user manual,

Compliance with European Union Directives

If this product has the CE mark, it is approved for installation within

the European Union and EEA regions. It has been designed and tested

to meet the following directives.

EMC Directive

This product is tested to meet Council Directive 89/336/EEC

Electromagnetic Compatibility (EMC) and the following standards,

in whole or in part, documented in a technical construction file:

EN 50081-2

EMC – Generic Emission Standard, Part 2 – Industrial Environment

EN 50082-2

EMC – Generic Immunity Standard, Part 2 – Industrial Environment

This product is intended for use in an industrial environment.