Knowledge Base

This does not apply to MMi203

The comms connector is a standard DB9. It provides an RS232 compatible interface. It is used for communications with a PC for programming and use with SPLatLink.

The RS232 interface is a basic interface with transmit data, receive data and ground. Pinouts are as follows:

PinSignal nameComments
1 Not connected
2RxDSerial data output from board
3TxDSerial data input to board
4 Not connected
5Gnd0V, signal ground
6DSRData Set Ready, switchable output line.
7 Not connected
8CTSHard-wired to +5V for accessory power
9 Not connected

This is a DCE (“looks like a modem”) interface, suitable for connection to a DTE, such as a computer, with a straight-through cable.

To connect the SPLat to another DCE, like a modem, you must use a crossover cable. The cable will need the following wiring:

pinpin
1 
2 RxD3 TxD
3 TxD2 RxD
4 
5 Gnd5 Gnd
6 DSR7 RTS
7 
8 CTS4 DTR
9 
Built in multi-drop capability

The interface has a special design that allows several boards’ interfaces to be connected in parallel, like pin to like pin. This makes possible small systems of up to 5 boards in a multi-drop communications configuration, connected perhaps to a shared modem. Please contact SPLat Controls for information about suitable Firmware to support this arrangement.

See also RS232 pinouts: A primer