I/O Ports - IBM 5170 Technical Reference

which bits are to be pulsed. A 0 indicates that the bit
should be pulsed, and a 1 indicates the bit should not be
modified.
Note: Bit 0 of the controller's output port is
connected to System Reset. Pulsing this bit resets the
microprocessor.
I/O Ports
The keyboard controller has two 8-bit 110 ports and two test
inputs. One of the ports is assigned for input and the other for
output. The controller uses the test inputs to read the state of the
keyboard's
I
clock
I
line and the keyboard's
I
data
I
line.
System Board 1-43