MMi202: Comms connector
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:
| Pin | Signal name | Comments |
|---|---|---|
| 1 | Not connected | |
| 2 | RxD | Serial data output from board |
| 3 | TxD | Serial data input to board |
| 4 | Not connected | |
| 5 | Gnd | 0V, signal ground |
| 6 | DSR | Data Set Ready, switchable output line. |
| 7 | Not connected | |
| 8 | CTS | Hard-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:
| pin | pin |
|---|---|
| 1 | |
| 2 RxD | 3 TxD |
| 3 TxD | 2 RxD |
| 4 | |
| 5 Gnd | 5 Gnd |
| 6 DSR | 7 RTS |
| 7 | |
| 8 CTS | 4 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