Honeywell 621-9929 (6219929) Product Description

621-9929 (6219929) is a Parallel Bus Selector module of the 621 series from Honeywell (Honeywell / ISSC), designed specifically for traditional DCS systems such as IPC 620/621, TDC 3000, TPS, etc., to achieve redundant switching of controller parallel buses, multi-master station arbitration, and signal routing, ensuring high availability at the system bus level.

I. Basic Information

Brand: Honeywell (Honeywell / ISSC)

Full Model: 621-9929 (6219929)

Series: 621 Series Bus Control Module (IPC 620/621, TPS)

Type: Parallel Bus Selector / Redundant Switching Module

Production Status: Obsolete (Out of Production)

Weight: Approximately 0.8 kg

Size: Approximately 6.0 × 27.3 × 17.5 cm

Installation: Inserted into the 621 series I/O rack

Power Supply: 5V DC (Backplane Bus Power Supply, typical 350 mA)

Common Suffix:

621-9929R: ** Hot Swap ** Version

621-9929R-RP: Refurbished / Repaired Version

II. Core Functions

Parallel Bus Redundancy: Dual-path parallel bus automatic millisecond-level switching, seamless seamless switch from main bus to backup in case of failure

Multi-master Station Arbitration: Supports 2 master controllers sharing I/O bus, without conflicting access

Bus Signal Routing: Parallel data high-speed forwarding between controller ↔ I/O rack

Bus Status Monitoring: Real-time monitoring of bus clock, data, check bits, break-line faults

Manual / Automatic Mode: Local manual switching + System automatic redundancy control

Electrical Isolation: Bus side - System side high-voltage electrical isolation

System Compatibility: Compatible with IPC 620/621, TDC 3000, TPS, PlantScape systems

III. Bus Specifications

Bus Type: 621 Parallel I/O Bus (16-bit data + Control / Address)

Redundant Channels: 2 independent parallel buses (primary / backup)

Switching Mode: Automatic Redundancy (Auto Failover), Manual Forced

Switching Time: < 5 ms (Fault Detection + Switch Completion)

Bus Clock Rate: 16 MHz

Data Width: 16-bit Parallel Data

Isolation Voltage: 2500V AC RMS (Bus - System Side)

Connector: 64-pin Euroconnector + 50-pin D-Sub

Protection: ESD, Overvoltage, Overcurrent, Reverse Polarity, Surge Protection

IV. Environmental Parameters

Operating Temperature: 0°C ~ +60°C

Storage Temperature: -40°C ~ +85°C

Humidity: 5–95% RH (No Condensation)

Anti-Vibration: 10–55 Hz, 0.7 mm Double Amplitude

Protection: IP20 (Installed in Cabinet)

Certifications: CE, UL, CSA, 94V-0 Flame Retardant

V. Interfaces and Status Indicators

Bus Interface: 2 × 64-pin Euroconnector (Primary / Backup Parallel Bus)

System Interface: 50-pin D-Sub (Controller Side)

LED Status:

PWR: Green (Power Supply Normal)

BUS A: Green (Primary Bus Active) / Red (Fault)

BUS B: Green (Backup Bus) / Red (Fault)

ACTIVE: Green (Current Selected Bus)

MANU: Yellow (Manual Mode) / AUTO: Green (Automatic Mode) ERR: Red (Bus Error / Check Failed)

Backplane Interface: 621 Rack-Specific Parallel Bus

VI. Typical Applications

DCS Controller Redundancy: IPC 620/621 Dual Master Controller Redundant Bus

Critical I/O High Availability: Safety I/O Bus for Chemical, Power, and Metallurgical Facilities

Old System Upgrade: 620/621, TPS Systems Add Bus Redundancy

Multiple Controllers Sharing: 2 Master Controllers Share the Same I/O Rack Resources

Distributed Control: Long-Distance Parallel I/O Bus Redundant Communication

VII. Model Comparison (621 Series Bus / Communication Module) Table

Parameters: 621-9929, 621-9928, 621-9000

Types: Parallel Bus Selector, Serial Link Selector, I/O Expansion Slave

Core Purpose: Parallel Bus Redundancy Switching, Serial Link Redundancy, Remote I/O Expansion

Channel Number: 2 Parallel Buses, 4 Serial Links, 1 RS-485

Switching Time: < 5 ms, < 10 ms, —

Isolation: 2500V AC, 2500V AC, 2500V AC

Adapted Bus: 621 Parallel I/O Bus, RS-232/485, RS-485 Master-Slave

VIII. Common Faults and Troubleshooting

Bus does not switch (AUTO ineffective)

Reason: No fault on the main bus, threshold not triggered, module configuration error

Troubleshooting: Check the bus clock/data signal, reconfigure the redundant parameters, restart the module

I/O communication interruption (after switching)

Reason: Backup bus failure, loose connection, address conflict

Troubleshooting: Test the backup bus, tighten the connectors, check the module address

ERR red light constantly on

Reason: Bus verification error, interference, module hardware failure

Troubleshooting: Replace the shielded cable, single-point grounding, replace the module for testing

IX. Related Models

Hot-swappable version: 621-9929R

Serial Link Selector: 621-9928 / 621-9928R

I/O Expansion Master: 621-9001

I/O Expansion Slave: 621-9000

Serial Communication Module: 621-9940 / 621-9938