Use the table below to find the current requirements of the devices 

using backplane power. Those devices that are not included in the 

backplane calculations are included in the example’s user-side calculations.

Selecting a User-Side Power Supply

You must provide a power supply that meets your system 

requirements. The following devices require user-side power:

• SLC Servo Module

• Encoders

• I/O modules

• Estop circuitry

• Fast inputs and outputs

You must select a power supply that meets the specifications of a NEC 

class 2 power supply. The power supply must have +5V, ±15V 

capacity, and +24V capacity for fast I/O and Estop circuitry.

Example of the Calculations for User-Side Current Requirements 

In this example, the system includes:

• One seven-slot modular rack

• One 1747-L541 CPU module

• One 1746-IB8 DC input module with eight inputs @ +24V

• One 1746-OV8 DC output module with eight outputs @ +24V

• An SLC Servo Module system that contains:

• Two SLC Servo Modules

• Two termination panels

• Two Allen-Bradley 845H encoders

• Six fast inputs

• Two fast outputs

Example of Calculations for Backplane Current Requirements 

In this example, the system includes:

• One seven-slot modular rack

• One 1747-L543 CPU module

• One 1746-IB8 DC input module with eight inputs @ +24V

• One 1746-OV8 DC output module with eight outputs @ +24V

• An SLC Servo Module system that contains:

• SLC Servo Modules

• Termination panels

• Allen-Bradley 845H encoders

• Fast inputs

• Fast outputs

Using Fast Inputs and Outputs

The fast I/O (FIN1through FIN3, and FOUT1) are 24V DC compatible 

and are used with a user-side +24V power supply. Review potential

24V DC I/O devices for compatibility with the electrical specifications 

as shown in the table below.

The SLC Servo Module operates in two modes:

• Configuration 

• Command 

When operating in the configuration or the command mode, the status 

of the module is reported to the SLC processor.

Configuration Mode Operation

You can enter configuration mode only if the system is in Estop. In the 

SLC Servo Module, you configure the SLC Servo Module by using M 

files containing data provided by the SLC 5/03 (or versions listed 

above) processors. All configuration parameters are internal to the SLC 

Servo Module and stored in non-battery backed RAM.

In configuration mode, you select the proper setup configuration to 

match the servo drive and motor without setting switches and without 

special software. If you do not set up your own configuration, the 

configuration is set to the default setting.

SLC Servo Module Operation

The SLC Servo Module, compatible with the SLC family, is used with 

SLC 5/03 FRN 5.0 (and above) processors using RSLogix 500, AI500 or 

APS (version 5.0 or higher) software. Once the SLC processor is 

initiated, the execution of the motion block is independent of the scan 

time of the processor. Blended motion allows for complicated move 

profiles consisting of two to thirty-two segments. The blended move 

profiles are stored in the SLC Servo Module’s memory as a series of 

absolute moves and can be executed more than once. Other move or 

homing operations can be performed between blended move profiles.

The SLC Servo Module controls absolute position over a range of 32 

bits. The SLC Servo Module performs an origin search (also called 

homing) and automatically resets the absolute position to the home 

position when the SLC processor requests a search function after 

detecting one of the following: 

• Encoder marker

• Limit switch

• Limit switch and marker

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.