7-6. I/O port map
8255 ON SUB CPU BUS
M / 3500
PA7
N.
DATAS '
PA6
DATAT
i‘A5 DATAS
PA4 DATA 5
PA3
Output
DATA4
8255
CÌ
PA2 DATAS
Printer
chip address(CX)11 /xxxx]
o
c
PAI
DATA2
>
PAO
>
DATAI
PC7
OBF outpu
ACK T-SET
Group A: Mode 1
Group B: Mode 0
PC6
ACK inputi
ACK
PC 5
N
STROBE ^
PC4
MUS 1 C , sustain
PC3
INTR NOT USE
PC 2
N
ACKC '
PCI
STC
Keyboard
PCO
DC
PB7
P/M
CG selection
O
PB6
SRDY
Sub CPU READY
o
c
T3
PB5
Output
CLK
ro
PB4
Din
PB3
C2
Clock
PB2
CI
PBl CO
PBO
STRB -
INPUT PORTC74LS2443
CDS7 :
HLT KEY
74LS244
CDS6D
STK D
Keyboard
port addressÌOlOO/xxxx]
CDS5D
DK J
CDS4D
PDTR -1
CDS33
PE
Printer
CDS23
BUSY J
CDSl 3
Reads the 8255 OBF (PC7)
COSO 3
output or timer output.
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