Radio Shack TRS-80 - Chapter 2: Expanding Programs; And the Program Grows

COLOR
COMPUTER
MEMORY
MAP
(cont'd)
FF00-FF03
PIA
U8
BIT
=
KEYBOARD
ROW
1
and
right
joystick
switch
BIT
1
=
KEYBOARD
ROW 2
and
left
joystick
switch
BIT
2=
KEYBOARD
ROW 3
FF00
|
BIT
3=
KEYBOARD
ROW
4
BIT
4=
KEYBOARD
ROW 5
BIT
5=
KEYBOARD
ROW 6
BIT
6=
KEYBOARD
ROW
7
BIT
7
=
JOYSTICK
COMPARISON
INPUT
Aura
t ,
/
0=1
RQ*
to
CPU
Disabled
Control
of
the
Horizontal
1=
|RQ*
to
CPU
Enabled
BIT1
sync
clock (63.5
microseconds)
^Fl^glet
on
the
falling
edge
of HS
Interrupt
Input
(
1=Rag
$et
Qn
the
rjsing
edge
of
HS
BIT
2
=
Normally
1
:
0=Changes
FF00 to
the
data
direction
register
BIT
3
=
SEL
1
:
LSB
of
the
two
analog
MUX
select
lines
FF01
{
BIT
4=
1
Always
BIT
5
=
1
Always
BIT
6 Not
Used
BIT
7
=
Horizontal
sync
interrupt
flag
BIT
0=
KEYBOARD
COLUMN
1
BIT
1=
KEYBOARD
COLUMN
2
BIT
2=
KEYBOARD
COLUMN
3
FF02 I
B,T
3=
KEYBOARD
COLUMN
4
BIT
4=
KEYBOARD
COLUMN
5
BIT
5=
KEYBOARD
COLUMN
6
BIT
6=
KEYBOARD
COLUMN
7
BIT
7=
KEYBOARD
COLUMN
8
''BIT©
BIT 1
0=IRQ*toCPU
Disabled
Control
of
the
field
sync
clock
\
-|=|RQ*toCPU
Enabled
16.667
Ms
Interrupt
Input
j
0=
sets
flag
on
falling
edge
FS
1=
sets
flag
on
rising
edge FS
FF03 I
BIT
2
=
NORMALLY
1
:
0=
changes
FF02
to
the
data
direction
register
BIT
3
=
SEL
2:
MSB
of the
two
analog
MUX
select
lines
BIT
4
=
1
Always
BIT5
=
1
Always
BIT
6 Not
Used
.BIT
7
=
Field
sync
interrupt
flag