Operations Of Port 4 - Fujitsu F2MC-8FX Hardware Manual

CHAPTER 9 I/O PORT
9.4.2

Operations of Port 4

This section describes the operations of port 4.
Operations of Port 4
Operation as an output port
• Setting the corresponding DDR bit to "1" sets a pin as an output port.
• For a peripheral function sharing pins, disable its output.
• When a pin is set as an output port, it outputs the value of the PDR to pins.
• If data is written to the PDR, the value is stored in the output latch and output to the pin as it is.
• Reading the PDR returns the PDR value.
Operation as an input port
• Setting the corresponding DDR bit to "0" sets a pin as an input port.
• For a peripheral function sharing pins, disable its output.
• If data is written to the PDR, the value is stored in the output latch but not output to the pin.
• Reading the PDR returns the pin value. However, the read-modify-write command returns the PDR
value.
Operation as a peripheral function output
• Setting the output enable bit of a peripheral function sets the corresponding pin as a peripheral function
output.
• The pin value can be read from the PDR register even if the peripheral function output is enabled.
Therefore, the output value of a peripheral function can be read by the read operation on PDR register.
However, the read-modify-write command returns the PDR value.
Operation at reset
• Resetting the CPU initializes the DDR value to "0", and sets the port input disabled.
Operation in stop mode and watch mode
• If the pin state specification bit in the standby control register (STBC:SPL) is set to "1" when the device
switches to stop or watch mode, the pin is set forcibly to the high-impedance state regardless of the
DDR value. Note that the input is locked to "L" and blocked in order to prevent leaks due to freed input.
• If the pin state specification bit is "0", the state remains in port I/O or peripheral function I/O and the
output is maintained.
Operation of the input level selection register
• Writing "1" to the bit0 of ILSR2 register changes the input level for Port4 from hysteresis input level to
automotive input level. When bit0 of ILSR2 register is "0", it becomes hysteresis input level.
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