Expansion Connector Pin Assignment

P0	Connected to pin P0 of EM120/EM200
P1	Connected to pin P1 of EM120/EM200
P6	Connected to pin P6 of EM120/EM200
P7	Connected to pin P7 of EM120/EM200
P8	Connected to pin P8 of EM120/EM200
GND	Ground
VCC	+5V from the EM120/EM200-EV board. Available "spare" current about 50mA
RST	Reset (active high) from the EM120/EM200-EV board. The signal is generated by an onboard reset IC. The same signal is applied to pin RST of EM120/EM200
MD	Connected to the download/setup button on the EM120/EM200-EV board. The signal is connected to pin MD of EM120/EM200
DTR	Connected to pin P3(DTR) of EM120/EM200
RTS	Connected to pin P5(RTS) of EM120/EM200
TX	Connected to pin TX of EM120/EM200
RX	Connected to pin RX of EM120/EM200
CTS	Connected to pin P4(CTS) of EM120/EM200
DSR	Connected to pin P2(DSR) of EM120/EM200

Output signals that are present both on the DB9M and expansion connectors (DTR, RTS, TX) need not be switched. So, for example, the TX (output) line from the EM120/EM200 is connected to the RS232 transceiver IC and to the expansion connector. For input signals (RX, CTS, DSR) there must be a way to disconnect the RS232 transceiver IC from the EM120/EM200. Three jumpers (combined with pins RX, CTS, DSR of the expansion connector) serve this purpose.

For example, when the RX jumper is closed the RX pin of the EM120/EM200 receives a signal from the RS232 transceiver. When the jumper is opened you can use the RX pin on the expansion connector to supply a TTL RX signal from your own external board. Figure below illustrates this.