Bachmann RS204 Serial Interface Module

The Bachmann RS204, also cataloged as the RS204 Serial Interface Module, operates as a dedicated hardware component for asynchronous serial data acquisition within the M200 controller backplane.

Hardware Specifications

Backplane Bus Communication Velocity

The RS204 integrates directly with the Bachmann M200 backplane bus architecture to execute high-speed serial data transfers. Engineers configure the module via software to select specific protocol standards, allowing mixed RS232, RS422, and RS485 configurations on a single module. The 128-byte FIFO buffer per port manages data flow, while the auto flow-control mechanism executes automatic handshakes to prevent buffer overruns. This deterministic backplane communication supports baud rates up to 1.5 MBaud for RS422 and RS485 links, ensuring low-latency data exchange between the M1/M200 controller and external field devices such as barcode scanners, HMIs, weigh scales, and legacy modems.

Frequently Asked Questions

Q: Can I mix different serial protocols on the same RS204 module?
A: Yes. Each of the four ports operates independently. You configure the protocol standard (RS232, RS422, or RS485) via software, allowing any combination of protocols across the four channels on a single module.

Q: How is the termination resistor managed for RS422 and RS485 links?
A: The module features integrated terminating resistors for RS422 and RS485 modes. You engage or disengage these resistors physically using the DIP switch located on the module, eliminating the need for external termination components at the module location.

Q: What is the galvanic isolation rating between the channels?
A: The module provides 500 V galvanic isolation between the system bus and each individual interface, as well as between the individual interfaces themselves. This prevents ground loops and protects the M200 backplane from voltage transients on the field wiring.

Field Installation Guidelines

1. Power Supply Verification: Verify that the external 24 VDC supply falls within the 18 VDC to 34 VDC range before inserting the module into the M200 backplane. The module draws approximately 120 mA at 24 VDC.
2. Termination Configuration: Before wiring RS422 or RS485 multidrop networks, locate the DIP switch on the RS204 module. Set the switch to the ON position to engage the integrated terminating resistors at the physical ends of the bus. Leave the switch OFF for point-to-point links or intermediate nodes.
3. Shield Grounding: Route serial communication cables away from high-voltage power conductors. Terminate the cable shield at the KZ 51/02 B terminal block using the shortest possible path to maintain signal integrity and comply with IEC 60664-1 Pollution Degree 2 requirements.
4. Environmental Limits: Confirm the ambient temperature within the control panel remains between -30 deg C and +60 deg C for standard units. If operating in environments with condensing humidity, verify the installed module carries the RS204 CC ColdClimate designation.
5. Software Configuration: After mechanical installation, access the Bachmann SolutionCenter or Device Manager to assign the specific protocol (RS232, RS422, RS485) and baud rate to each individual channel before commissioning the serial link.