Serial Line Controller
Overview
The serial line controller handles four asynchronous serial lines.
The DC7085 chip is used as the serial line controller. The DC7085
directly controls an external 64-entry silo shared by all four
receive lines. Access to the DC7085 by the CPU and interrupt
processing for the DC7085 are controlled by the CEAC. The four
serial lines are numbered 0 through 3, and each has a particular
primary use, as described in Table 1–7.
Table 1–7 Serial Line Usage
Line
Device
Description
0
Keyboard
Connected to a 15-pin D-sub connector
1
and to a 4-pin
modular jack mounted on the system board. Data leads
only. Supports the LK401 keyboard.
1
Pointer
Connected to a 15-pin D-sub connector
1
and to a miniature
DIN connector mounted on the system board. Data leads
only. Supports VSXXX-AA mouse or VSXXX-AB tablet.
2
Communications
Connected to a 25-pin D-sub connector mounted on the
system board, RS423 compatible. Data leads plus modem
control signals.
3
Printer
Connected to a 6-pin modified modular jack mounted on the
system board. DEC423, data leads only.
1
Same connector
Line 3 is normally connected to a printer through a BC16E cable.
If a switch, accessible from the front of the system enclosure, is
set to enable, a received break condition on this line asserts the
CPU halt signal, which causes a processor restart with a restart
code of 2.
1–29
