Mouse Connector
---------------
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)
Keyboard Connector
------------------
Pin Name Description, Notes
1 CGNB Chassis ground
2 KBD1 Keyboard clock
3 KBD2 Keyboard data
4 +5V
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
Modem and Printer Ports
-----------------------
Pin Signal name Signal description
1 HSKo Handshake out
2 HSKi Handshake in/external clock
3 TXD- Transmit data -
4 GND Signal ground
5 RXD- Receive data -
6 TXD+ Transmit data +
7 NC General purpose input*
8 RXD+ Receive data +
- Connector type: 8-pin minicircular
SCSI Port (25-pin)
------------------
Pin Signal name Signal description
1 REQ/ Request
2 MSG/ Message
3 I/O/ Input/Output
4 RST/ SCSI bus reset
5 ACK/ Acknowledge
6 BSY/ Busy
7 GND Signal ground
8 DB0/ Data bit 0
9 GND Signal ground
10 DB3/ Data bit 3
11 DB5/ Data bit 5
12 DB6/ Data bit 6
13 DB7/ Data bit 7
14 GND Signal ground
15 C/D/ Common/Data
16 GND Signal ground
17 ATN/ Attention
18 GND Signal ground
19 SEL/ Select
20 DBP/ Data parity
21 DB1/ Data bit 1
22 DB2/ Data bit 2
23 DB4/ Data bit 4
24 GND Signal ground
25 NC No connection
- Connector type: DB-25
- Total length of all cables not to exceed 6 m (20 ft.)
WARNING: The SCSI port uses the same type of connector as a standard RS-232,
DB-25 serial interface, but it is different electrically. Do not connect any
RS-232 device to this connector. Doing so can result in damage to both the
device and the Macintosh Classic.
Audio Output Port
-----------------
Pin Signal name Signal description
(Sleeve) GND Signal ground
(Tip) AUDIO .5 volt peak-to-peak
audio signal
- Connector type: Miniature mono phone plug
- The internal speaker is disabled when this port is in use.