Sharp MZ-80B Owner's Manual page 58

49
4.3.1 Signal system for the 8255 block
The 8255 (Programmable peripheral interface) is responsible for control of automatic cassette
deck, reverse operation of CRT display, blank control, memory switching between IPL state and nor-
mal state, output control of source pulse for generating sound, and lighting control of keyboard LEDs.
FIGURE 4.8 summarizes the signal system for the 8255.
Keyboard
RVS
LED
GRPH
SFT LOCK
8255
PA 7
Cassette control
PA
6
PA
5
D7
8
PA
4 I
STOP
PAs
Do
PLAY PA
2
FF. REW ready PA
1
MOTOR ON PA
0
A.
Write data
PC 7
Ao
RD/WR
PC
6
FF. REW latch
PC,
-
EJECT
PC
4
RD
PCs
-
WR
PC
2
Read data
PC
1
RESET
Set ready
r - -
PC
0
cs
Pawl provided/not
t - -
~
PB 7
PB
6
PB,
Display
I
Sound
PB
4
Control
....
PBs
-..
PB
2
REVERSE
--
PB
1
Compulsory-BLANK
I
PB
0
V-BLANK
+5VGND
SOUND GATE
SEL MEMORY [
BOOT/ NORMAL
PIO B
7
FIGURE 4.8
Signal
system for the 8255 block