Honeywell 621-9938R Serial I/O Module

Overview

The Honeywell 621-9938R Serial I/O Module (SIOM) provides reliable serial communication for UCN systems, including TDC 3000. It links remote I/O card files with processor card files through high-speed serial channels. The module ensures robust data transfer and supports redundant operation when paired with the 621-9939 SLM. Engineers use it in distributed control applications where stability and scalability are critical.

Technical Specifications

• Model: 621-9938R

• Manufacturer: Honeywell

• Module Type: Serial I/O Module (SIOM)

• Communication Protocols: RS-232, RS-485, optional CAN in some setups

• Input Voltage: 24 VDC

• Current Consumption: Approx. 300 mA

• Dimensions: 1.5" × 10.5" × 6.5" (3.8 × 26.7 × 16.5 cm)

• Weight: 1.85 lbs

• I/O Capacity: Supports 8, 16, or 32-point configurations

• Redundancy Support: Dual communication ports; interfaces with 621-9939 SLM

• DIP Switch Settings:

• SW1: Starting address (0–2032, increments of 8)

• SW2: Fault response and test mode

• SW3–SW5: I/O points per slot

• Termination Requirements: 200 or 300 Ω resistors at channel ends

• Installation Notes:

• Install in slot N of remote serial I/O card file

• Use Serial Link Selector 621-9928R for dynamic switching

• Do not mix 8/16-point modules in 32-point slots