Radio Shack TRS-80 Service Manual page 12

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1/0
port
(LH5811)
Pin Signal
In/out Connection Functional description
No.
Name
I PAI In/out
Key
Port A input/output. Key strobe.
~ ~
~ ~
~
7
PA7
In/out
Key
Port A input/output, Key strobe.
8
GND
In
Power
OV
9
PBO
In/out Option Port B input/output
JO PB I In/out OptiOll
Port B input/output
11
PB2
In CMTIN Port ll input/output. Cassette tape data input..
12
PJ~3
In
GNO
Domestic}export spe. c ification select pin
(Domestic)
VCC
(Export)
13 P84 In GND
Use.r area dctcnnination pin
14
P\l:5 In µP0!990C
Clock input from TP tenninal of t he timer JC
I S Pll:6 In µPOl990C
Data input from the DA TA OUT tem1inal of •he timer IC
16 PIP In Key
BREAK key input (interrupt input)
17
P¢
In GND
PC port latch clock input
18
PC'O
Out
µPD 1990C
Data output t o the DA TA IN tem1inal to the timer IC
19 PCI Out µPDl990C Sirobc output to the STB tenninal fo the timer IC
20
PC2 Out µP01990C
Clock output to the LK tenni.nal of the tirner IC
21
PC3
Out µPD1990C
Tinier IC control signal output
22
PC4
Out µPDl990C Timer IC control signal output
23
PCS Out
µPD1 990C
Timer IC control signal output
24
PC6 Out
Buzzer
2S
PC7
26
cso
In CPU Chip select input connected to AD12
27
CS!
In CPU
Chip select input connected
10
AD13
28 CS2 In
Decoder IC
Chip select input connected to Y3 of the chip select decoder
IC
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