CHAPTER 4 PORT FUNCTIONS
User's Manual U11919EJ3V0UM00
73
4.2.3 Port 2
This is a 3-bit I/O port with output latch. Port 2 can be specified in the input or output mode in 1-bit units by using
the port mode register 2 (PM2). When using P20 to P22 pins as input port pins, on-chip pull-up resistors can be
connected in 3-bit units by using the pull-up resistor option register (PUO).
The pins of this port are also used as the data I/O and clock I/O pins of the serial interface.
RESET input sets port 2 to input mode.
Figures 4-4 through 4-6 show the block diagrams of port 2.
Caution
When using the pins of port 2 as the serial interface, the I/O mode and output latch must be set
according to the function to be used. For details of the settings, see Table 9-2.
Figure 4-4. Block Diagram of P20
Internal Bus
V
DD0
P-ch
P20/ASCK/SCK0
WR
PUO
RD
WR
PORT
WR
PM
PUO2
Alternate
Function
Output Latch
(P20)
PM20
Alternate
Function
Selector
PUO : Pull-up resistor option register
PM
: Port mode register
RD
: Port 2 read signal
WR : Port 2 write signal
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