Epson manual Other Computers with Nonstandard Serial Ports, MFJ-1278B RS-232C Computer RS-232C

MFJ-1278B MULTI-MODE COMPUTER INTERFACING

If your computer is configured as DCE, you will have to wire pin 2 of your MFJ-1278B to pin 3 of the computer RS-232C connector. Then wire pin 2 of the computer's RS-232C connector to pin 3 of your MFJ-1278B. Please note that pin 7 of the computer's RS-232C connector will still connect to pin 7 of your MFJ-1278B serial port. Some computers may require that pin 5 of the computer serial port connector be connected. Others may require connections for pin 8 and pin 20. You can use the computer's output signals on pins 4 and 6 as shown in Fig. 2-3.

MFJ-1278B RS-232C	Computer RS-232C
2	2
3	3
7	7
	4
	5
	6
	8
	20

Fig. 2-3. Serial port wiring with jumpers for

auxiliary signals.

Other Computers with Nonstandard Serial Ports

Computers with non-standard serial ports must meet the following conditions.First, the signal levels should be RS-232C compatible. The MFJ-1278B requires that the voltage levels sent from the computer be greater than about +3 volts in one state and less than about +1 volt in the other state.

Second, the polarity of the signals must conform to the RS- 232C standard. This means that the low voltage state must correspond to a logical "1" and the high voltage state to a logical "0".

Third, the computer must be able to correctly receive a signal that meets the RS-232C specification. The MFJ-1278B supplies signals that meet this specification.

Make or buy a cable that provides the following connections. The common pin on the computer's RS-232C serial port must be connected to pin 7 on the MFJ-1278B serial port. Connect the line that sends data from the computer to pin 2 on the MFJ-1278B RS-232C port. Connect the line that your computer receives data on to pin 3 on the MFJ-1278B RS- 232C port.