2 +5V +5 V Supplied by Mac - only supplied on Macs before the PLUS
3 GND Ground
4 TXD+ Data being transmitted from the Mac is on this line(positive format)
5 TXD- Data being transmitted from the Mac is on this line(negative format(normal))
6 +12V +12V Supplied by Mac
7 HS Handshake - this line is used to tell the Mac the peripheral is ready to receive*
8 RXD+ Data being received by the Mac is on this line(positive format)
9 RXD- Data being received by the Mac is on this line(negative format(normal))
* this line will be “High” or +12 V to indicate that the peripheral is ready
also note +- 12 V is a maximum voltage for the interface. You will find the actual voltages will range from about 8 to 12 V, more often than not 10V.
8 PIN MINI DIN
PIN SIGNAL DESCRIPTION
1 GND Ground
2 GND Ground
3 TXD+ Data being transmitted from the Mac is on this line(positive format)
4 TXD- Data being transmitted from the Mac is on this line(negative format(normal))
5 +12V +12V Supplied by Mac
6 HS Handshake - this line is used to tell the Mac the peripheral is ready to receive*
7 RXD+ Data being received by the Mac is on this line(positive format)
8 RXD- Data being received by the Mac is on this line(negative format(normal))
You will notice that the +5V line was dropped. This was the line that killed the original Thunderscan. This is an optical scanner that is placed into the Imagewriter to scan a page. The Thunderscan ran off of that +5V supply. When the +5V was removed people had to upgrade!
If you ask... Why was not the +12V removed? The best answer I can give is it is a “logical” signal that can be used in connection(as you can see later in this document).
MINIMUM OUTPUT LINES NEEDED FOR A CONNECTOR WITH THE MAC
Pin 1 of the Mac is connected to pin 3 of the Mac. TXD-, RXD-,HS,GND are all that are needed
PIN SIGNAL DIRECTION
1 GND Ground reference
5 TXD- Output from Mac
7 HS Input to Mac
9 RXD- Input to Mac
Pins of 25 pin D connector for a peripheral device.
The big eight pins(and one more line) as paraphrased from
The RS-232 Solution
by Joe Campbell
Published by Sybex Computer Books
ISBN#0-89588-140-3
If the book is not in stock at your local book store you may find a similar book. Or order the book using this information above.
(sorry if it is out of print)
This book is a must read for anyone seriously into connecting the Mac to anything. Although it is not Mac specific but it explains the RS-232 concepts. The book presents the information clearly. It is easy to understand as well as read.
Pin Name Description
1 GND GND
2 TXD Receive Data-Input
3 RXD Transmit Data-Output
4 CTS Clear to Send-input to indicate the computer is “ready”
5 RTS Request to Send- output to indicate the peripheral is “ready”
6 DSR Data Set Ready-output to indicate the peripheral is “ready”
7 GND GND
8 DCD Data Carrier Detect-I am not sure
20 DTR Data Terminal Ready-show that either the perif. is ready or the computer
Some lines vary from machine to machine
If this section of these notes confuses you I recommend getting the book(although not strongly, it is confusing!)
HERE IS A GENERAL CATCH AL MAC TO RS-232 25 PIN D CONNECTOR
Mac 25 pin D connector
Pin Signal Pin Signal
1 GND 1 GND
3 GND 7 GND
5 TXD to 2 RXD from
6 Mac is ready 4 Is Mac ready?(this is the +12V line)
7 Perif. ready? 5 Perif. is ready
9 RXD from 3 TXD to
pin 20 of the 25 D connector is an alternate Perif. ready signal.
EXAMPLES OF CONNECTORS:(I use)
MAC OUTPUT TO IMAGEWRITER I INPUT
MAC PRINTER MAC
PIN SIGNAL PIN PIN
3 GND 7 8 GND is connected to 3 pins
5 TXD- 3
7 HS 20
8 RXD+ 7 3 GND is connected to 3 pins
9 RXD- 2
please note I have know idea why the RXD+ is tied to ground! But it is!
MAC TO ADC PHONE-MODEM 1200 BAUD
MAC TO 25 PIN D connector
PIN SIGNAL PIN
1 GND 1 1 + 3, 1 + 7 can be connected at each connector
3 GND 7 so you use 1 instead of 2 wires
5 TXD- 2
7 Handshake 20
9 RXD- 3
MAC TO APPLIED READER TECHNOLOGY EPROM PROGRAMMER
(which I purchased through Jameco Electronics for about $180)
Mac Signal EPP-1
1 GND 7
5 TXD- 2
7 Handshake 5
9 RXD- 3
Also connected were
Pin 1 of Mac to pin 3 of Mac. Pin 6 of programmer to pin 4 of programmer
Or alternately
MAC TO APPLIED READER TECHNOLOGY EPROM PROGRAMMER
Mac Signal EPP-1 Signal
1 GND 1 GND
3 GND 7 GND
5 TXD- 2 RXD
6 Mac is ready 4 Is Mac ready?(this is the +12V line)
7 Device ready? 5 Device is ready!
9 RXD- 3
I have been having a little of trouble with this device(ever since I used it on an IBM(makes you wonder)). It won’t stop being written to, so I am forced to unplug the thing. If anyone knows why or how to fix this I would appreciate the info.
Please note I disclaim everything! Although I have tried to correctly inform you of all the information I know on the subject, I don’t know it all! continue with standard disclaimer whatever that is. You know, I am not responsible for the action you take because of this doc etc...
This is freeware and not to be sold for profit.
Good Luck
Happy connections
Thomas Walsh
Address:
ThomasW4
American Online
Other notes by the Author:
SID Assembly Help-Tips in constructing Cedar Tech’s Sound input device. To make it look more professional, and make the job go easier(I hope). It also contains a correction to the supplied documentation notes.
