Radio Shack TRS-80 Model 100 - Page 47

&3
PAo_
7
(
8
>
(Input/Output)
PB.-,(8)
(Input/Output)
PCo_
s
(6)
(Input/Output)
These
8
pins
are general
purpose
I/O
pins.
The
in/out
direction
is selected
by programming the
command
register.
These
8
pins are general
purpose
I/O
pins.
The
in/out
direction
is selected
by programming
the
command
register.
These
6
pins
can
function as
either
input
port,
output
port,
or
as
control
signals for PA and
PB.
Programming
is
done
through
the
command register.
When
PC
_
s
are
used
as
control
signals,
they
will provide
the following:
PC
-
A
INTR (Port
A
Interrupt)
PC,
-
ABF (Port
A
Buffer
Full)
Pd
-
A STB (Port
A
Strobe)
PC
3
-
B INTR (Port
B Interrupt)
PC
4
-
B BF (Port
B
Buffer
Full)
PCs
-
B STB (Port
B Strobe)
TIMER IN
(Input)
Input
to the counter-timer.
TIMER
OUT
(Output)
Timer
output.
This output
can
be either
a
square
wave
or a
pulse
depending
on the timer
mode.
Vcc
+5 volt
supply.
Vss
Ground Reference.