smh@mhuxl.UUCP (henning) (04/04/86)
**** ****
From the keys of Steve Henning, AT&T Bell Labs, Reading, PA mhuxl!smh
I recently completed connecting a printer buffer between a Mac+ and an
ImageWriter II. I was surprised to find out how Apple chose to make
its 8-pin circular cable. Since I have interfaced the Mac+ to a
number of DB-25 (RS232) peripherals I am posting this documentation.
The following is the pinout of the stock Mac+ cables and custom cables
I made to use the Mac+ with a Hayes modem and a printer MicroBuffer:
First, I will show the connector pin assignments:
_____ _________________
/ V \ | |
/ 8 7 6 \ \ 1 2 3 4 5 /
| 5 4 3 | \ 6 7 8 9 /
> 2 1 < \___________/
\ _____/
Mac+ "mini-circular" DB-9 Connector
8-pin connector
_____________________________________________________
| |
\ 1 2 3 4 5 6 7 8 9 10 11 12 13 /
\ 14 15 16 17 18 19 20 21 22 23 24 25 /
\_______________________________________________/
DB-25 Connector
============================================================================
The stock 8-pin circular cable to connect the ImageWriterII looks like:
ImageWriterII(8-pin)---(M0187 Apple System/Peripheral-8 Cable)---(8-pin)Mac+
M0187 Circular-8 to Circular-8 "Apple System/Peripheral-8 Cable"
8-pin 8-pin Yes ladies and gentlemen, this cable
1 2 is not a conventional 1 goes to 1 etc.
2 1 cable but one of apples better ideas
3 5 for the rest of us. If you check
4 4 carefully you will see that this cable
5 3 is symmetric and will work regardless
6 8 of which way you plug it in.
7 7
8 6
shield shield
==============================================================================
The stock cable to connect the Mac+ to earlier Mac cables looks like:
Mac+(8-pin)---(Apple Part 699-0372 Mac+ Peripheral Adapter)---(DB-9)Peripheral
Apple Part 699-0372 "Mac+ Peripheral Adapter Cable"
8-pin DB-9
1 7 DTR/DSR
2 6 DSR/DTR
3 9 TxD-/RxD-
4 3 SG
5 5 RxD-/TxD-
6 8 TxD+/RxD+
7 N/C
8 4 RxD+/TxD+
shield 1 PG
=============================================================================
My custom cable to connect my Hayes SmartModem 1200 was also used on the
output of the Microbuffer and looks like this:
ImageWriterII(8-pin)-(#699-0372)-(DB-9)-(custom cable A)-(DB-25)Printer Buffer
Mac+ (8-pin)-(#699-0372)-(DB-9)-(custom cable A)-(DB-25)Hayes SmartModem 1200
custom cable A
DB-9 DB-25
1 1
2 N/C
3 7*
4 N/C
5 2
6 20
7 8
8 7*
9 3
==========================================================================
The second custom cable I had to make to connect the MicroBuffer was:
Mac+ (8-pin)-(#699-0372)-(DB-9)-(custom cable B)-(DB-25)Printer MicroBuffer
custom cable B
DB-9 DB-25
1 1
2 N/C
3 7*
4 7*
5 3
6 8
7 20
8 N/C
9 2