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IV-8.
I/O
Address
Map
ADDRESS
BIT
CONTENTS
CONTROL
OOH
Key
scan data
Read/Write
UART
CONTROLLER
10H
82C51
character
data
Read/Write
11H
82C51
control/status data
Read/Write
TIMER
20H
Timer
counter
Write
only
21H
Timer
counter
1
Write only
22
H
Timer
counter
2
Write
only
23H
Timer
control
word
Write
only
PRINTER
30H
Printer
data out
port
Write
only
31
bit
7
Printer strobe out port
Write
only
32
H
bitO
Printer
Busy
read port
Read
only
32
H
bit?
Printer
/Busy
read
port
Read
only
INTERRUPT/NMI
CONTROL
(setting
interrupt
mask
control)
50H
bitO
Timer
counter
0/ON. 1/OFF
hit!
Serial
RXRDY
0/ON, 1/OFF
bit2
Low
battery
0/ON, 1/OFF
bit
3
External
interrupt
(setting
NMI
mask
control)
0/ON. 1/OFF
bit4
DC/DC
power
off
0/ON. 1/OFF
bit5
Back-up
battery
low
(showing
interrupt status)
0/ON. 1/OFF
5011
bitO
Timer
counter
0/ON. 1/OFF
bill
Serial
RXRDY
0/ON. 1/OFF
bit2
Low
battery
0/ON. 1/OFF
bit 3
External
interrupt
(showing
NMI
mask
control)
0/ON, 1/OFF
bit4
DC/DC
power
off
0/ON, 1/OFF
bit
5
Back-up
battery
low
0/ON, 1/OFF
MEMORY
BANK
CONTROL
51H
bit()-4
Write/Read
select
ROM
bank
i
number
bit5-7
Write/Read
select
RAM
bank number
SYSTEM STATUS REGISTER
(Write
Register)
52H
bitO
DC/DC
power
control
0/ON, 1/OFF
bitl
Beep
control
0/OFF.
1/ON
bitb
LCD
power
control
0/OFF.
1/ON
bit?
Main
battery
select
(Read
Register)
O/Ni-Cd.
1
/Alkaline
52H
bitO
Power
switch show-
0/ON, 1/OFF
bill
Beep
status
show
0/ON. 1/OFF
bit2
RS232C
CD
status
0/ENABLE. 1/DISABLE
CASSETTE
CONTROL
(Read
port)
53H
bilO
Read
output data
bit?
Read
input
data
(Write
port)
53H
bit?
Timer
counter
1
set
0/DISABLE,
1/ENABLE
54H
hi
tO
Remote
motor
control
0/OFF,
1/ON
4-7
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