[net.micro.apple] IIc Serial Port Description

jrw@hropus.UUCP (James R. Webb) (12/31/85)

>I would like to interface a U.S. Robotics Auto Dial 212A modem with
>an Apple IIc.

>Here is the pin-out for the modem:

> 2 Transmit Data, terminal to modem (TD)
> 3 Receive Data                     (RD)
> 5 Clear to Send                    (CTS)
> 6 Data Set Ready                   (DSR)
> 7 Signal Ground                    (GND)
> 8 Carrier Detect                   (CD)
>12 Speed Indicate
>20 Data Terminal Ready              (DTR)
>22 Ring Indicator

>Can anyone give me info on how to make a cable to the IIc serial
>port?

First off, this is the pinout for the IIc's serial ports:

                              1 - Data Terminal Ready      (DTR)
      5 O           O 1       2	- Transmit Data Output     (TD)
        4 O       O 2         3	- Power and Signal Ground  (GND)
              O               4	- Read Data Input          (RD)
              3               5 - Data Set Ready           (DSR)
	
I am always wiring null modems to connect hardwired terminals, and
they reverse everything, but I think (!) that since you are connecting
the IIc to a modem, you just connect DTR to DTR, TD to TD, etc...
You probably have to jumper 1 and 7 on the modem end together and run them
to 3 on the IIc as they are both grounds.
-- 
James R. Webb                                   ihnp4!houxm!hropus!jrw