Signals Around The 8255; Cassette Controller - Sharp MZ-700 Service Manual

a) Signals around the 8255
The 8255 Programmable Peripehral I/O Controller assumes
the control of the cassette recorder, CRT screen cursor
Port
PA
($EOOO)
PB
($EOOl)
PC·
($EOO2)
Cassette
control
Key data
input terminal
(8P)
RDATA
MOTOR
M·ON
WDATA
Key data
strobe terminal
(lOP)
Port terminal
PA o
PAl
PA
2
PA
3
PA
7
PB o
PB
I
PB
2
PB
3
PB
4
PB s
PB
6
PB
7
PC
I
PC
2
PC
3
PC
4
PC s
PC
6
PC
7
r - - -
' -
VBLNK
5560UT
INTMSK
556RST
0
LS
0
\
145
-
C
B
9
A
I/O
Active state
H
OUT
H
L
L
IN
L
OUT
-
OUT L
OUT 51..
IN H
IN
-
IN
-
IN
-
blinking timing, keyboard scan strobe output, and key
return data.
8255
PBO
\
0,
PB7
\
Do
PC7
PC6
AI
PC2
PC5 Ao
PC4
PC3
RD
PCl WR
CS
PA7
RESET
PA,
PA.
PAl
PA o
Control function
} Keyboud scan stwhe
slgnal
output
Cursor blinking timer reset
Keyboard scan data input
Cassette data write
•
Timer interrupt disable
Motor rotate control
Motor rotation check
Cassette data read
Cursor blinking timer input
Vertical blanking
0,
AI
8255
RESET
Signal name
556RST
WDATA
INTMSK
M-ON
MOTOR
RDATA
5560UT
VBLNK
• Output data handled in the bit cell mode. (Port C in control mode)
b) Cassette controller
Data transfer with the cassette recorder is carried out on
PCI, PC4, and PC5 of the 8255. Shown next is the data
format (Sharp PWM method) of the cassette tape.
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