Overview
Manuals
Parallel Link Role
Address Switches
Source Boundary
Features:
- Honeywell manual names exact 621-9937 as PIOM.
- Documented 50-pin parallel link supports local rack daisy chaining.
- SW1 and other switch banks configure rack and slot addresses.
Honeywell's February 1988 IPC 620-25/35 User Manual describes the local parallel I/O path from the processor's Parallel Link Driver Module to a PIOM in the 621 I/O rack. It identifies 621-9937 in the switch-setting section. A 50-pin D connector links the processor and PIOM, while a second PIOM port can carry the connection to another rack. The manual specifies a 100-foot maximum data cable length for this local configuration. These statements establish a system arrangement, not independent signal-processing or isolated I/O specifications for the PIOM.
The PIOM switch settings determine rack starting address and slot allocations. The manual says SW1 switches 1 through 8 set the starting address in increments of eight, while other switch banks allocate zero, eight, sixteen or thirty-two addresses to each rack slot. Before service, record the physical module and revision, rack identity, IN/OUT cabling, every switch position, all installed I/O cards and the resulting address map. Follow approved isolation and ESD procedures. After a verified replacement, check rack communication and all affected input and output points. Do not copy generic serial-I/O module specifications onto this parallel interface.
The 621-9937 Honeywell IPC 620 Parallel I/O Module may still be available for purchase and support from Moore Automated Company beyond End-Of-Life (EOL) by the manufacturer (OEM).
Honeywell 621-9937 documentation and reference links.
Honeywell-authored February 1988 IPC 620-25/35 manual page 23 names 621-9937 PIOM and its address configuration; third-party mirror.
Honeywell describes the PIOM as the rack-side interface for local parallel I/O. The processor's Parallel Link Driver connects to it by a 50-pin D cable, and additional racks can be daisy-chained through the other PIOM port. Check the actual host rack, cable direction, connector condition and module marking; a serial I/O card is a different device.
The manufacturer says 621-9937 SW1 sets each I/O rack's starting address in increments of eight. Other switch banks select how many addresses belong to each slot, from zero through thirty-two. A replacement must preserve the full rack and slot map, not just its own visible switch pattern. Record the installed cards and project configuration before moving hardware.
The 1988 Honeywell manual supports exact 621-9937 PIOM identity and the documented 620-25/35 parallel-I/O topology. Its 100-foot cable and 2048-point figures describe the system arrangement, not the PIOM's weight, isolated-channel count or network bit rate. Current hardware revision, stock condition and compatibility require a physical label and site records in addition to this older PDF.
