DSEAH@WPI.BITNET (04/21/88)
Ok, ok. Here is what I REALLY meant to say. In our last episode, Dave was struggling with unfamiliar terms. A newcomer to communications still baffled by RS232 lingua technica, he tries to make a GS to external modem cable. But lo, the back of the reference book says: PRINTER and MODEM PORTS Pin# Signal descriptions Pin# Signal description -------------------------------------------------------- 1 Handshake out 5 Receive data minus 2 Handshake in 6 Transmit data plus 3 Transmit data minus 7 Goes to DCD input on SCC 4 Signal ground 8 Receive data plus The terms are strangely familiar, yet so different. The plus and minus stuff make the very ground upon which he stands tremble in uncertainty. A kind soul suggested that the minus was for RS422 communications. So what is the correspondence to a RS232 DB25 connector? +---------------------------------------------------------------------------+ | Dave Seah --- Worcester Polytechnic Institute | +-----------------------------------------------+---------------------------+ | Bitnet: DSeah@WPI.Bitnet | We can't receive files! | | Internet: DSeah%WPI.Bitnet@CUNYVM.CUNY.EDU | EMAIL only! Apples Rock! | +-----------------------------------------------+---------------------------+
denbeste@bgsuvax.UUCP (William C. DenBesten) (04/22/88)
> So what is the correspondence to a RS232 DB25 connector?
If you can find a gs (or Mac +) to ImageWriter ONE cable, you have the
cable that you need.
Mini Name Imagewriter I
Din-8 (db25)
1 HSKo --> DSR 6
2 HSKi <-- DTR 20
3 TxD- --> RxD 3
4 GND = GND 7,8 (sGND,DCD)
5 RxD- <-- TxD 2
6 Txd+
7 n.c.
8 Rxd+ = GND 7 ground to simulate RS232
Note: I have not actually tried this. I don't build cables with the
mini din 8 connectors myself. They are too small to solder easily.
It turns out that apple uses RS422 serial protocol, not RS232 serial
protocol. RS422 can be made to emulate RS232 by grounding the
positive receiver and leaving the positive transmitter disconnected.
See Inside Macintosh, volume 3 chapter 2 for more complete details. I
suspect that the GS Hardware reference manual would cover this also,
but the gs is my home toy, not my work toy.
I am not interested in debating RS422 vs RS232, so don't flame apple's choice.
--
William C. DenBesten | denbeste@bgsu.edu
Dept of Computer Science | CSNET denbeste%andy.bgsu.edu@relay.cs.net
Bowling Green State University | UUCP ...!cbosgd!osu-cis!bgsuvax!denbeste
Bowling Green, OH 43403-0214 |scott@hpuslma.HP.COM (Jim Scott) (04/22/88)
Dave, All I did to hook up my Hayes modem was to wire three pins as follows: Apple IIGS Connector Hayes Connector 3 TD- 2 4 SG (signal ground) 7 5 RD- 3 I also tied pins 4 & 8 togetAher in the IIGS connector to prevent noise problems. Anyway this set up has worked very well. I believe that the TD+ and RD+ pins are used primarily for the Appletalk networking scheme. Jim
kamath@reed.UUCP (Sean Kamath) (04/24/88)
In article <8804201709.AA06818@wpi.local> DSEAH@WPI.BITNET writes: >A kind soul suggested that the minus was for >RS422 communications. > >So what is the correspondence to a RS232 DB25 connector? > >| Dave Seah --- Worcester Polytechnic Institute | Well, you can use rs-422 with rs-252 by only using the minus pins. Let me hope I'm right here, but the Mac and GS use the same serial controller, and are both rs-422, and I recall that this is what we did. I.e. use -TxD and -Rxd to got to TxD and RxD on the 232 device, and sig ground to sig ground, case to case. >PRINTER and MODEM PORTS > >Pin# Signal descriptions Pin# Signal description >-------------------------------------------------------- >1 Handshake out 5 Receive data minus >2 Handshake in 6 Transmit data plus >3 Transmit data minus 7 Goes to DCD input on SCC >4 Signal ground 8 Receive data plus so, in more or less "standard" jargon, pin one and two are general hanshake lines, which go high or low to signal busy. They have no direct equivilant in rs-232. Pin 6 and 8 likewise have no equiv. in 232. Pin 3 and 5 are 232 pins 2 and 3 (or 3 and 2. THis is the biggest bogus situation I've ever seen. Cables should have a switch on them saying "swap 2 and 3".) four is seven, and I'm not sure what 7 is. Also, what is SCC? I assume it is Serial Comunications something, or some such. If it goes to Data Carrier Detect, then it probably is high. Sean Kamath OK, so this is somewhat confusing. I have built a cable that goes from mini-8 to DB25. But unless I know the whole story, I get a little confused. I'm not *possitive* the mac and GS use the *exact* same cabling. If it does, and poeple want more descriptive text, I'll be glad to do it right. -- UUCP: {decvax allegra ucbcad ucbvax hplabs ihnp4}!tektronix!reed!kamath CSNET: reed!kamath@Tektronix.CSNET || BITNET: reed!kamath@PSUVAX1.BITNET ARPA: reed!kamath@psuvax1.arpa US Snail: 3934 SE Boise, Portland, OR 97202 (I hate 4 line .sigs!)
whitney@think.COM (David Whitney) (04/25/88)
In article <1956@bgsuvax.UUCP> denbeste@bgsuvax.UUCP (William C. DenBesten) writes: >> So what is the correspondence to a RS232 DB25 connector? > >If you can find a gs (or Mac +) to ImageWriter ONE cable, you have the >cable that you need. I'm not entirely sure, but I think that this won't work, unless you want to connect to a printer. If you want to connect to a modem, spring the $15 for a Mac+ to Hayes cable. If you say that to the sales guy, there is no way he can screw up and give you the wrong kind of cable. David Whitney, MIT '90 Still learning about my Apple //GS {the known universe}!ihnp4!think!whitney and all of its secrets. Any and all whitney@think.com technical info appreciated. DISCLAIMER: If they only knew what I was doing and saying here...