STC12C5Axx
Technical Summary
17
Functional Description
I/O Port Configuration
There are 44(max) port pins on STC12C5Axx may be independently configured to one of four
modes: quasi-bidirectional(standard 8051 port output), push-pull output, open-drain output or
input-only. All port pins default to quasi-bidirectional after reset. Each port pin has a
Schmitt-triggered input for improved input noise rejection. During power-down, all the
schmitt-triggered inputs are disabled with the exception o
f P3.2 (INT0) and P3.3 (INT1) or
RXD_PIN to drive this device escape power-down mode. Therefore such kind of pins should not be left
floating during power-down.
There are several special function registers designed to configure those I/O ports.
SFR:
P0M0
(P0 Configuration 0)
Read/Write
Address:
0X94H
Default: 0000-0000
Bit
7
6
5
4
3
2
1
0
Name
P0M0.7
P0M0,6 P0M0.5
P0M0.4
P0M0.3
P0M0.2
P0M0.1 P0M0.0
SFR:
P0M1
(P0 Configuration 1)
Read/Write
Address:
0X93H
Default: 0000-0000
Bit
7
6
5
4
3
2
1
0
Name
P0M1.7
P0M1,6 P0M1.5
P0M1.4
P0M1.3
P0M1.2
P0M1.1 P0M1.0
SFR:
P1M0
(P1 Configuration 0)
Read/Write
Address:
0X92H
Default: 0000-0000
Bit
7
6
5
4
3
2
1
0
Name
P1M0.7 P1M0,6 P1M0.5
P1M0.4
P1M0.3
P1M0.2
P1M0.1 P1M0.0
SFR:
P1M1
(P1 Configuration 1)
Read/Write
Address:
0X91H
Default: 0000-0000
Bit
7
6
5
4
3
2
1
0
Name
P1M1.7
P1M1,6 P1M1.5
P1M1.4
P1M1.3
P1M1.2
P1M1.1 P1M1.0
SFR:
P3M0
(P3 Configuration 0)
Read/Write
Address:
0XB2H
Default: 0000-0000
Bit
7
6
5
4
3
2
1
0
Name
P3M0.7
P3M0,6 P3M0.5
P3M0.4
P3M0.3
P3M0.2
P3M0.1 P3M0.0
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