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CHAPTER 5 PORT FUNCTIONS
5.5 Port 3
Port 3 is an 8-bit input/output port with an output latch. Input/output can be specified bit-wise by means of the port 3 mode
register (PM3).
In addition to its function as an input/output port, port 3 also has various dual-function control signal pin functions.
The operating mode can be specified bit-wise by means of the port 3 mode control register (PMC3), as shown in
Table 5-5. The pin level of all pins can always be read or tested regardless of the dual-function pin operation.
When RESET is input, port 3 is set as an input port (output high impedance state), and the output latch contents are
undefined.
Table 5-5. Port 3 Operating Modes
(n = 0 to 7)
Mode
Port Mode
Control Signal Input/Output Mode
Setting Condition
PMC3n = 0
PMC3n = 1
P30
Input/output port
TO10 output
P31
TO11 output
P32
RxD/SI1 input
P33
TxD/SO1 output
P34
ASCK input/SCK1 input/output
P35
RxD2/SI2 input
P36
TxD2/SO2 output
P37
ASCK2 input/SCK2 input/output
(a) Port mode
Each port specified as port mode by the port 3 mode control register (PMC3) can be specified as input/output bit-
wise by means of the port 3 mode register (PM3).
(b) Control signal input/output mode
Pins can be set as control pins bit-wise by setting the port 3 mode control register (PMC3).
(i) TO10, TO11 (Timer Output)
These are timer output pins of timer 1.
(ii) RxD, RxD2 (Receive Data)
These are serial data input pins of the asynchronous serial interface.
(iii) TxD, TxD2 (Transmit Data)
These are serial data output pins of the asynchronous serial interface.
(iv) SI1, SI2 (Serial Input)
These are serial data input pins of the 3-wire serial I/O.
(v) SO1, SO2 (Serial Output)
These are serial data output pins of the 3-wire serial I/O.
(vi) ASCK, ASCK2 (Asynchronous Serial Clock)
These are external baud rate clock input pins.
(vii) SCK1, SCK2 (Serial Clock)
These are serial clock I/O pins of the 3-wire serial I/O.