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Figure 18.2 shows a block diagram of the 4-bit general-purpose I/O port.
Internal bus
PDTRW
PORTEN
0: Port not available 1: Port available
PBnPuP
0: Pull-up
DnDIR
0: Input
PBnIO
0: Input
PBnPUP
PORTEN
Dn output data
D Q
C
BCK
DnDIR
PBnIO
Data input strobe
0
1
Dn input data
1: Pull-up off
1: Output
1: Output
Figure 18.2 4-Bit Port
0
1
0
1
C
Q D
Pull-up resistor
Port 19 (input/
output)/D51
to
Port 16 (input/
output)/D48
BCK
Rev. 4.0, 04/00, page 641 of 850
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