Specifications

CHAPTER 1
Introduction
Serial I/O Ports 13
Serial I/O Ports 1
The Macintosh LC 520 computer has two serial ports, one for a printer and one for a
modem. The printer port uses the standard 8-pin mini-DIN socket. The modem port uses
a 9-pin mini-DIN socket. Both sockets accept 8-pin plugs, but only the modem port
accepts a 9-pin plug. Figure 1-6 on page 14 shows the mechanical arrangement of the pins
on the serial port sockets; Table 1-4 on page 14 shows the signal assignments.
Table 1-3 Pin assignments for the internal floppy disk connector
Pin
number Signal name Signal description
1 GND Ground
2 PH0 Phase 0: state control line
3 GND Ground
4 PH1 Phase 1: state control line
5 GND Ground
6 PH2 Phase 2: state control line
7 GND Ground
8 PH3 Phase 3: register write strobe
9 n.c. Not connected
10 /WRREQ Write data request
11 +5V +5 volts
12 SEL Head select
13 +12V +12 volts
14 /ENBL Drive enable
15 +12V +12 volts
16 RD Read data
17 +12V +12 volts
18 WR Write data
19 +12V +12 volts
20 n.c. Not connected