Sharp MZ-700 - Page 133

4.3.1 Signal system of the 8255
The 8255 outputs keyboard scan signals, input key data, and controls the cassette tape deck and cursor
blink timing.
Ke
ter
y data in put
mina I
(8 P)
.--------
~
\IBLK
5560UT
INTMSK---
Data recorder
control
~
R
M- ONi
WDA TA
.
556RST
eyboard scan
K
sig
te
(1
nal output
rminals
OP)
r---
~-
0
LS
1--
\1 45~
A
9
I
8255
PBo
D7
I
PB1
I
Do ,
PC 1
PC s A1
PC 2
PC5
Ao
PC 4
PC a
RD
PC1
WR
CS
PA1
RESET
PAa
PA2
PA1
PAo
D7
I
Do
Ao
EM R
MW
CSEO
8255
RESET
Port Terminal
1/0
Active state Description
of control
Name
of signal
PA
0
H
) Keyboard scan signals
PA
PA
1
H
($EOOO)
PA
2
OUT H
PA
3
H
J
PA
7
L
Resets
the cursor blink timer.
556 RST
PB
0
L
PB1
L
PB
2
L
PB PB
3
IN
L
Key scanning data input signals
($E001)
PB4
L
PB
5
L
PB6
L
PB
7
L
PC
1
OUT
-
Cassette tape write data
WDATA
PC
2
OUT
L
Inhibits clock interrupts. INTMSK
PC*
PC3
OUT
_n_
Motor drive signal
M-ON
($E002)
PC
4
IN
H Indicates that the motor is on.
MOTOR
PC
5
IN
-
Cassette tape read data RDATA
PC
6
IN
- Cursor blink timer input signal 556 OUT
PC
7
IN
-
Vertical blanking signal VBLK
* Each
output data bit can be independently set or reset.
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