At 12:42 PM 8/28/96, Wada, Tatsuaki wrote:
>Here are the Pin Assignments for DIN-8 and IBM DB-9. I found them in the
>Apple Technical Information Library.
>
>
>     Circular 8      Signal                             IBM DB-9
>        1       HSKo (+12V)                             1 DCD
>        2           HSKi                                2 RxD
>        3           TXD-                                3 TxD
>        4           GND                                 4 DTR
>        5           RXD-                                5 SG
>        6           TXD+                                6 DSR
>        7           No Wire                             7 RTS
>        8           RXD+                                8 CTS
>        GND                                             9 Ring Indicator

Some background info:  the RS-232 standard is between a modem with a female
DB-25 connector on its case and a terminal with a male connector at the end
of a cable.  For the standard everything that isn't a modem (including a
computer) is a terminal, so we get all kinds of confusion when you want to
connect a computer to a terminal or printer.  On the standard 25-pin
connector:
 8      DCD     Data Carrier Detect     Modem to Computer/Terminal
 3      RxD     Receive Data            Modem to Computer/Terminal
 2      TxD     Transmit Data           Computer/Terminal to Modem
20      DTR     Data Terminal Ready     Computer/Terminal to Modem
 7      SG      Signal Ground
 6      DSR     Data Set Ready          Computer/Terminal to Modem
 4      RTS     Request To Send         Computer/Terminal to Modem
 5      CTS     Clear To Send           Modem to Computer/Terminal
22      RI      Ring Indicator          Modem to Computer/Terminal

DCD means the modem is connected to another modem at the other end of the
phone line.
DTR means the Computer/Terminal is turned on.
DSR means the Modem is turned on.
RTS means the Computer/Terminal wants to send data.
CTS means the Modem says it's OK to send data.

For a set-up with no hardware flow control you can wire DTR, DSR, and DCD
together and wire RTS to CTS.  I do not recommend this.

I could swear that there is a ready signal in each direction on that 8-pin
connector on the Mac.  Try looking for some more complete information.
Bill Studenmund is the source of all knowledge on serial port stuff if you
have trouble.

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