Allen-Bradley SLC 500 1746 Modules – 1746-HSTP1 Stepper Control Module

Technical Dossier

Product Details And Specifications

Allen-Bradley SLC 500 (1746) Series Technical Notes

The Evolution of SLC 500 / 1746 Architecture

The SLC 500 family was introduced by Allen-Bradley in the late 1980s as a successor to the SLC 100 and SLC 150 fixed-format controllers. The 1746 modular I/O standard was established to allow flexible rack-based expansion, separating the processor from I/O in a way that the earlier fixed-chassis designs could not support. Early processors such as the SLC 5/01 (1747-L511) operated at 1K word program memory with no communication port beyond DH-485. Successive generations added DH+ (SLC 5/04), Ethernet/IP (SLC 5/05), and expanded memory up to 64K words. The 1746 I/O modules evolved in parallel: early discrete modules used fixed 24VDC or 120VAC ratings, while later generations introduced HART-capable analog modules, high-speed counter inputs, and specialty motion modules including the 1746-HSTP1 stepper controller. By the mid-2010s, Rockwell Automation formally transitioned new designs toward the CompactLogix (1769) and ControlLogix (1756) platforms. The SLC 500 / 1746 series entered a sustained maintenance phase. Rockwell's official end-of-life notices for many 1746 modules have driven demand for third-party and surplus inventory sources to support installed base continuity.

SLC 500 / 1746 Full Catalog & Functionalities (SKU List)

Stepper & Motion Control

• 1746-HSTP1: Single-axis open-loop stepper motor controller, pulse/direction output, up to 250 kHz step rate, SLC 500 backplane interface.

High-Speed Counter / Encoder Input

• 1746-HSC: Dual-channel high-speed counter module, up to 1 MHz input frequency, quadrature encoder support.
• 1746-QS: Quadrature/pulse input module for position feedback, 4-channel, 100 kHz per channel.

Analog Input Modules

• 1746-NI4: 4-channel analog input, ±10V / 0–20 mA / 4–20 mA selectable, 12-bit resolution.
• 1746-NI8: 8-channel analog input, voltage/current configurable per channel, 12-bit.
• 1746-NI16I: 16-channel current input module, 4–20 mA, single-ended, 12-bit.
• 1746-NI16V: 16-channel voltage input module, ±10V, single-ended, 12-bit.
• 1746-NT4: 4-channel thermocouple/mV input, supports J, K, T, E, R, S, B types.
• 1746-NR4: 4-channel RTD input, supports Pt100, Pt1000, Ni120, 10Ω Cu.

Analog Output Modules

• 1746-NO4I: 4-channel current output, 4–20 mA, 12-bit resolution.
• 1746-NO4V: 4-channel voltage output, ±10V / 0–10V, 12-bit resolution.

Discrete Input Modules

• 1746-IA16: 16-channel AC input, 100–120VAC, isolated groups.
• 1746-IB16: 16-channel DC input, 10–30VDC, sink/source compatible.
• 1746-IB32: 32-channel DC input, 10–30VDC, high-density format.

Discrete Output Modules

• 1746-OB16: 16-channel DC output, 10–50VDC, 0.5A per point, sourcing.
• 1746-OW16: 16-channel relay output, Form A contacts, 2A per point, 240VAC/30VDC.
• 1746-OB32: 32-channel DC output, 10–50VDC, high-density sourcing.

Communication Modules

• 1746-BAS: BASIC module for custom ladder-integrated BASIC language programming and serial communication.
• 1746-DNET: DeviceNet scanner module, supports up to 63 nodes, explicit and I/O messaging.

Processor Modules

• 1747-L511: SLC 5/01 processor, 1K word memory, DH-485 port.
• 1747-L541: SLC 5/04 processor, 16K word memory, DH+ and DH-485 ports.
• 1747-L551: SLC 5/05 processor, 64K word memory, Ethernet/IP and DH-485 ports.

Quality Control for the SLC 500 / 1746 Range

The 1746 backplane uses a proprietary parallel bus architecture with time-multiplexed I/O scanning. Quality verification for 1746 modules requires backplane-level functional testing, not bench-level continuity checks alone. DriveKNMS testing procedures for this series include: full rack insertion and backplane communication handshake verification using a reference SLC 5/04 or 5/05 processor; channel-by-channel I/O functional test under rated load conditions; for analog modules, calibration verification against NIST-traceable references at 0%, 50%, and 100% of rated range; for the 1746-HSTP1 specifically, step pulse output verification at 1 kHz, 50 kHz, and 250 kHz with oscilloscope capture; firmware revision identification and logging; and visual inspection of backplane edge connector pins, conformal coating integrity, and capacitor condition. All tested units are issued a DriveKNMS inspection report with test date, technician ID, and pass/fail criteria documentation.