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4.10 Port 8
4.10.2 Operation of Port 8
This section describes the operations of port 8.
I
Operation of Port 8
H
Operation as an output port
If "1" is set to the corresponding DDR8 register bit, the port becomes an output port.
The operation of the output transistor is allowed when port 8 operates as an output port and
data of the output latch is output to the pins.
If data is written into the PDR8 register, the data is retained on the output latch and then
output directly to the pins.
Pin values can be read by reading the PDR8 register.
H
Operation as an input port
If "0" is set to the corresponding DDR8 register bit, the port becomes an input port.
The output transistor is "OFF" and the pins are in high impedance when port 8 operates as
an input port.
If data is written into the PDR8 register, the data is retained on the output latch but is not
output to the pins.
Pin values can be read by reading the PDR8 register.
H
Operation during resource I/O
Set "0" to the DDR8 register corresponding to the resource input pin to use port 8 for
resource input.
H
Operation during a reset
If CPU is reset, the value of the DDR8 register is initialized to "0". Thus, the output transistor
is turned "OFF" (input port) and the pins are put into high impedance.
The PDR8 register is not initialized by a reset. Thus, to use port 8 as an output port, output
data must be set to the PDR8 register and the output must be set to the corresponding
DDR8 register.
The ADEN1/CIER registers are initialized to "1" by a reset. Thus, to use port 8 for port input,
"0" must be set to the corresponding bits of the ADEN1/CIER registers.
H
Operation in stop mode and watch mode
If the pin state designate bit (STBC: SPL) of the standby control register is set to "1" when a
transition to the stop mode or watch mode occurs, the pins are put into high impedance
because the output transistor is forced "OFF" regardless of the value of the DDR8 register.
The input other than that of P84 is fixed to prevent leakage due to input opening.