Sharp MZ-80B - Signal System for the Z80 A-PIO Block

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4.3.3 Si gnal system f or th e ZSOA-PIO block
The
Z80 A- PIO (Parallel Inp ut/ O ut put interface contr oller) is responsible for ou tput of the strobe
sig nal for keyboard scan, input of key dat a, setting the key strobe to low l ev el, address switching for
V-R
AM and o ut put of th e 40/80 character mode se lecti on cont rol signa l.
FIGURE 4 .1 0 summarizes the signal system for the Z80A-PIO.
Key dat a
input terminal
8
po rts
Port B
hand s hak e
r-
"====
I
r-t-
Key str o be
out put term inal
12 po rts
PortA
hand s hak e
'--
R
SEL V-RAM AD
SEL V-RAM AD
SEL 40 CHR /8 0C
R
HR
r--
154
1..-
PIO
D,
B,
I
8
B•
Do
/
B,
B.
B•
B/A SEL
B,
B,
C/ D SEL
Bo
B
ROY
B STB I ORQ
RD
A,
A•
CE
,--
A,
Ml
A•
A,
A,
A,
Ao
ARDY
lEI
vlf\11
A STB
lEO
INT
4>+5V GND
r r i
FIGURE 4.10 Signal system for the PIO
A,
Ao
[
+5V]
~
~
Data bus
PIO co nt rol
Ml
RESET
Interrupt
co ntrol