Specifications

CHAPTER 3
I/O Features
22 Serial I/O Ports
This chapter describes both the built-in I/O devices and the interfaces for external I/O
devices. It also describes the types of external video monitors that can be used with the
Macintosh Performa 6400 computer.
Serial I/O Ports 3
The Macintosh Performa 6400 computer has two serial ports, one for a printer and one
for a modem. Both serial ports have 9-pin mini-DIN sockets that accept either 8-pin or
9-pin plugs. Both serial ports support the GeoPort serial protocol. Figure 3-1 shows the
mechanical arrangement of the pins on the serial port sockets; Table 3-1 shows the signal
assignments.
Figure 3-1 Serial port sockets
Table 3-1 Serial port signals
Pin Name Signal description
1 HSKo Handshake output
2 HSKi Handshake input (external clock on modem port)
3 TxD– Transmit data –
4 Gnd Ground
5 RxD– Receive data –
6 TxD+ Transmit data +
7 GPi General-purpose input (wakeup CPU or perform DMA handshake)
8 RxD+ Receive data +
9 +5V +5 volts to external device (100 mA maximum)
Printer Modem
8 7
1
5 4
2
39
68 7
1
5 4
2
39
6