Overview
The Honeywell MU-TSIM12 51303932-426, also identified by the base model MU-TSIM12, provides serial Modbus RTU communication between Honeywell APM/HPM systems and compatible field devices. It supports EIA-232 and EIA-485 interfaces, asynchronous bidirectional transmission, and configurable serial communication parameters for data exchange with Modbus-compatible equipment.
Hardware Specifications
| Parameter | Specification |
|---|---|
| Model | MU-TSIM12 |
| Spare Part Number | 51303932-426 |
| Brand | Honeywell |
| Origin | USA |
| Product Type | Serial Interface I/O Processor / FTA |
| Communication Protocol | Modbus RTU |
| Serial Interfaces | EIA-232 / EIA-485 |
| Baud Rates | 1200, 2400, 4800, 9600, 19200 bps |
| Data Format | 8 data bits with programmable 9th bit |
| Parity | None, odd, or even |
| Stop Bits | 1 |
| Transmission Mode | Asynchronous, bidirectional |
| RS-232 Distance | 15 m maximum |
| RS-485 Distance | 1.2 km maximum |
| RS-485 Drops | 15 maximum per FTA |
| Devices per SI | 2 FTAs per SI |
| Devices per FTA | Up to 15 |
| Data Capacity | 16 points per serial channel |
| Supported Data Types | Booleans, reals, signed integers, ASCII strings |
| Supported Function Codes | 01, 02, 03, 04, 05, 06, 08, 16 |
| Message Response Timeout | Configurable; 1.5 seconds listed as the default |
| Intermessage Stall Time | Minimum 3.5 character times |
| Surge Withstand | ANSI/IEEE C37.90.1-1978 |
| ESD Protection | IEC 801.2 |
Serial Communication and Modbus RTU Characteristics
The MU-TSIM12 supports two physical serial interface standards. EIA-232 provides separate transmit, receive, and modem-control signals, including TXD, RXD, RTS, CTS, DSR, DTR, and DCD. The maximum specified cable distance is 15 m, subject to a cable capacitance limit of 2500 pF.
For EIA-485, the interface uses a two-wire differential pair, Data+ (B) and Data- (A), with protective ground for the shield. The interface operates in half-duplex mode, supports up to 15 drops, and specifies a maximum device distance of 1.2 km. The stated common-mode operating capability is 250 VAC RMS continuous.
The Modbus RTU interface supports function codes 01, 02, 03, 04, 05, 06, 08, and 16. In addition, the module supports Boolean values, real numbers, signed integers, and ASCII strings. Each serial channel provides 16 points, with supported data quantities organized into arrays within the APMM/HPMM system.
Frequently Asked Questions (FAQ)
Q: Which serial communication interfaces does the MU-TSIM12 support?
A: It supports EIA-232 and EIA-485. EIA-232 has a specified maximum distance of 15 m, while EIA-485 supports up to 1.2 km under the stated specifications.
Q: How many Modbus devices can the interface support?
A: Each SI supports two FTAs, with up to 15 devices per FTA. The EIA-485 interface also specifies a maximum of 15 drops.
Q: Which Modbus RTU communication settings are configurable?
A: The module supports baud rates of 1200, 2400, 4800, 9600, and 19200 bps; none, odd, or even parity; selectable modem control; and configurable message response timeout and keep-alive cell write settings.
Field Installation Guidelines
- Confirm the selected serial interface matches the connected device and the configured Modbus RTU communication parameters.
- For EIA-232, observe the specified 15 m maximum distance and the 2500 pF cable capacitance limit.
- For EIA-485, use a suitable two-wire differential cable and observe the specified 1.2 km maximum distance and 15-drop limit.
- Route serial communication cables separately from high-voltage and high-current conductors to reduce electromagnetic interference.
- Apply a consistent cable shield grounding arrangement appropriate to the system design. Avoid unintended ground loops.
- Verify device addresses, baud rates, parity, stop bits, response timeout, and supported function codes before commissioning.
- Check the applicable Honeywell system documentation for FTA wiring, module installation, power requirements, and system compatibility. Do not assume hot-swap support without model-specific confirmation.
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