Pin Name Description, Notes
1 CGND Chassis ground
2 +5V See hardware Description, Notes for power limits
3 CGND Chassis ground
4 X2 Horizontal movement line (connected to VIA PB4 line)
5 X1 Horizontal movement line (connected to SCC DCDA-
line)
6 N-C Not connected
7 SW- Mouse button line (connected to VIA PB3)
8 Y2 Vertical movement line (connected to VIA PB5 line)
9 Y1 Vertical movement line (connected to SCC DCDB- line)
Macintosh Keyboard Connector
Pin Name Description, Notes
1 CGNB Chassis ground
2 KBD1 Keyboard clock
3 KBD2 Keyboard data
4 +5V
Macintosh External Drive Connector
Pin Name Description, Notes
1 CGNB Chassis ground
2 CGND Chassis ground
3 CGND Chassis ground
4 CGND Chassis ground
5 -12V
6 +5V
7 +12V
8 +12V
9 N-C Not connected
10 PWM Regulates speed of the drive
11 CA0 Control line to send commands to the drive
12 CA1 Control line to send commands to the drive
13 CA2 Control line to send commands to the drive
14 LSTRB Control line to send commands to the drive
15 WrReq- Turns on the ability to write data to the drive
16 HdSel Control line to send commands to the drive
17 Enbl2- Enables the Rd line (else Rd is tristated)
18 Rd Data actually read from the drive
19 Wr Data actually written to the drive
Macintosh RS422 9 Pin Communications Connectors
The following pin connections apply to the interfaces for both the serial
communications modem port and the serial printer port on the Macintosh 128K
and 512K. If the device being connected to the Macintosh
uses RS422 the cable must have pins 4 and 8. If the device uses RS-232
pins 4 and 8 are not necessary.
DB-9 Connector Pin Signal Name Comments
RS-232: RS-422:
1 GND GND Ground
2 Not used +5V Don't use this one; it may
be converted into output
handshake in later equipment
3 GND GND Ground
4 Tx+ Tx+ Transmit Data, positive going
component
5 Tx- Tx- Transmit data, negative going
component
6 +12V +12V Use this one only to detect
Macintosh power on, not as a
power source.
7 DSR HSK Handshake input. Signal name
depends on the mode: Used for
Flow Control or Clock in.
8 Rx+ Rx+ Receive Data, positive going
component
9 Rx- Rx- Receive Data, negative going
component
NOTE:
Macintosh uses pin 7 as an input when communicating to printers in order
to determine whether the printer is ready to receive data (DTR hardware
handshaking). Macintosh uses software handshaking for connecting to
remote computers or terminals.
The signal range for RS-422 communication is 2 to 6 volts. Refer to EIA
Standard RS-422 available from:
EIA Engineering Department
2001 Eye St. N.W.
Washington, D.C. 20006