Single-Chip Microcontrollers User's Manual

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CHAPTER 6 PORT FUNCTIONS
P-ch
WR PM
WR PORT
RD
WR
PUO
V DD
Selector
PUO2
Output Latch
(P20, P21, P23 to P26)
PM20, PM21
PM23 to PM26
Internal bus
Dual Function
P20/SI1,
P21/SO1,
P23/STB,
P24/BUSY,
P25/SI0/SB0/SDA0,
P26/SO0/SB1/SDA1
Figure 6-6. Block Diagram of P22 and P27
PUO : Pull-up resistor option register
PM : Port mode register
RD : Port 2 read signal
WR : Port 2 write signal