> I want to connect a MAC with a 16C74 via a serial line. I intend to > transmit only some ascii sequences through the line. But I'm not a > Mac user and so I have some questions. If you're not a Mac user, why are you using a Mac? Apparent contradiction? :-) > * Which software (terminal progam) can I use to transmit the ascii sequences? You can get kermit via ftp from watsun.columbia.edu > * I want to use only two lines (TxD and GND) between the Mac and the PIC. Ok? If you build the PIC hardware & software correctly, sure. > * Can I use the same schematic like in AN 547 (RS-232 interface)? Can't find my Embedded Applications Handbook right now, so I can't comment on this. However, the Mac uses an RS-422 style differential signal on a miniDIN-8 connector. Apple chose voltages such that it is compatible with RS-232 signaling levels. miniDIN-8 connector 1 HskO handshake out 6 7 8 2 HskI handshake in / external clock 3 TxD- transmit data minus 3 4 5 4 Grd signal ground 5 RxD- receive data minus 1 2 6 TxD+ transmit data plus 7 no connection male end, looking at pins 8 RxD+ receive data plus I make Mac to RS-232 DTE (ready to plug into a modem) cables as follows: miniDIN-8 DB25P male HskO 1 --------------- 4 + 20 RTS + DTR HskI 2 --------------- 5 CTS TxD- 3 --------------- 2 TxD Grd 4 --------------- 7 SG RxD- 5 --------------- 3 RxD TxD+ 6 (n.c.) 7 (n.c.) RxD+ 8 --------------- 7 SG Note that Mac pins 4 & 8 both go to DB25P pin 7. So for your project, you'd only need to wire Mac pins 3 & 4 to your PIC. Lee Jones ------------------------------------------------------------------- Jones Computer Communications lee@frumble.claremont.edu 509 Black Hills Dr, Claremont, CA 91711 voice: 909-621-9008 -------------------------------------------------------------------