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18.2.3
Port Control Register B (PCTRB)
Port control register B (PCTRB) is a 32-bit readable/writable register that controls the input/output
direction and pull-up for each bit in the 4-bit port (port 19 pin to port 16 pin). As the initial value
of port data register B (PDTRB) is undefined, each bit in the 4-bit port should be set to output with
PCTRB after writing a value to the PDTRB register.
PCTRB is initialized to H'00000000 by a power-on reset. It is not initialized by a manual reset or
in standby mode, and retains its contents.
Bit:
Initial value:
R/W:
Bit:
Initial value:
R/W:
Bit:
Initial value:
R/W:
Bit:
PB19PUP PB19IO PB18PUP PB18IO PB17PUP PB17IO PB16PUP PB16IO
Initial value:
R/W:
Bit 2n + 1 (n = 0–3)—Port Pull-Up Control (PBnPUP): Specifies whether each bit in the 4-bit
port is to be pulled up with a built-in resistor. Pull-up is automatically turned off for a port pin set
to output by bit PBnIO.
Bit 2n + 1: PBnPUP
0
1
Rev. 4.0, 04/00, page 652 of 850
31
30
—
—
0
0
R
R
23
22
—
—
0
0
R
R
15
14
—
—
0
0
R
R
7
6
0
0
R/W
R/W
Description
Bit m (m = 16–19) of 4-bit port is pulled up
Bit m (m = 16–19) of 4-bit port is not pulled up
29
28
—
—
0
0
R
R
21
20
—
—
0
0
R
R
13
12
—
—
0
0
R
R
5
4
0
0
R/W
R/W
27
26
—
—
0
0
R
R
19
18
—
—
0
0
R
R
11
10
—
—
0
0
R
R
3
2
0
0
R/W
R/W
25
24
—
—
0
0
R
R
17
16
—
—
0
0
R
R
9
8
—
—
0
0
R
R
1
0
0
0
R/W
R/W
(Initial value)
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