Radio Shack TRS-80 Service Manual page 13

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1/0 port
(LH581 1)
Pin Signal
Inf out
Connection Funclional description
No.
Name
29
RSO
In CPU Internal register and operation stlcct signal
l
l
?
~
l
32 RS3 In CPU Internal register and 0peration select signal
33
R/W
In CPU
Read/write input
34 MEI In
CPU Memory enable
35 MEO In
CPU Memory enable and 1/0 port controller enable
36
WO In Option Wait condition input
37
WI
In Option Wah condition input
38 GND In Power
ov
39
vcc
In
Power +SY
40
DMEI Out Decoder
ROM enable
4 1
DMEO Out
ROM, option ROM enable
42
WAIT
Out
CPU
Wait signal to the CPU
43 INT Out CPU Interrupt request to the CPU
44
RESET In RF.SET circuit ln_ i tial reset signal
45
IRQ
In Option
Jntcrrupl request input
46 ¢OS
In CPU Basic clock input
47
CLI CLO
Not used. Serial data receptjon clock input
48 SDI
(VCC)
Not used. Serial data reception input
49
LC
NC Not used. LCD dri.er synchronizing signal
50 CLO In CLI Serial data transmission/reception clock
51
SDO
In CMT Serial transmission & reception data. Use for the cassette
tape data output.
52 DO
lnjout
CPU Data bus
?
~
~
~
?
59 D7 lnjout CPU
Data bus
60
PAO
Out
Koy
Port A input/output. Used as the key st robe.
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