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7.4
Port 3
7.4.1
Overview
Port 3 is an 8-bit input/output port which also functions as a data bus. It's pin configuration is
shown in figure 7.3. Port 3 is a data bus in modes 1 to 5 (expanded modes) and a generic
input/output port in modes 6 and 7 (single-chip mode).
Pins in port 3 can drive one TTL load and a 90-pF capacitive load. They can also drive a
darlington transistor pair.
Port 3
7.4.2
Register Descriptions
Table 7.5 summarizes the registers of port 3.
Table 7.5
Port 3 Registers
Address *
Name
H'EE002
Port 3 data direction register
H'FFFD2
Port 3 data register
Note: * Lower 20 bits of the address in advanced mode
176
Port 3 pins
Modes 1 to 5
P3 /D
D
7
15
15
P3 /D
D
6
14
14
P3 /D
D
5
13
13
P3 /D
D
4
12
12
P3 /D
D
3
11
11
P3 /D
D
2
10
10
P3 /D
D
1
9
9
P3 /D
D
0
8
8
Figure 7.3 Port 3 Pin Configuration
Modes 6 and 7
(input/output)
P3 (input/output)
(input/output)
P3 (input/output)
(input/output)
P3 (input/output)
(input/output)
P3 (input/output)
(input/output)
P3 (input/output)
(input/output)
P3 (input/output)
(input/output)
P3 (input/output)
(input/output)
P3 (input/output)
Abbreviation
R/W
P3DDR
W
P3DR
R/W
7
6
5
4
3
2
1
0
Initial Value
H'00
H'00
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