MB95650L datasheet(35/105 Pages) CYPRESS

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Document Number: 002-04696 Rev. *A

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MB95650L Series

15.1.4 Port 0 operations

Operation as an output port

• A pin becomes an output port if the bit in the DDR0 register corresponding to that pin is set to “1”.

• For a pin shared with other peripheral functions, disable the output of such peripheral functions.

• When a pin is used as an output port, it outputs the value of the PDR0 register to external pins.

• If data is written to the PDR0 register, the value is stored in the output latch and is output to the pin set as an output port as it is.

• Reading the PDR0 register returns the PDR0 register value.

Operation as an input port

• A pin becomes an input port if the bit in the DDR0 register corresponding to that pin is set to “0”.

• For a pin shared with other peripheral functions, disable the output of such peripheral functions.

• When using a pin shared with the analog input function as an input port, set the corresponding bit in the A/D input disable register

(lower) (AIDRL) to “1”.

• If data is written to the PDR0 register, the value is stored in the output latch but is not output to the pin set as an input port.

• Reading the PDR0 register returns the pin value. However, if the read-modify-write (RMW) type of instruction is used to read

the PDR0 register, the PDR0 register value is returned.

Operation as a peripheral function output pin

• A pin becomes a peripheral function output pin if the peripheral output function is enabled by setting the output enable bit of a

peripheral function corresponding to that pin.

• The pin value can be read from the PDR0 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 the PDR0 register. However, if the read-modify-write (RMW) type

of instruction is used to read the PDR0 register, the PDR0 register value is returned.

Operation as a peripheral function input pin

• To set a pin as an input port, set the bit in the DDR0 register corresponding to the input pin of a peripheral function to “0”.

• When using a pin shared with the analog input function as another peripheral function input pin, configure it as an input port by

setting the bit in the AIDRL register corresponding to that pin to “1”.

• Reading the PDR0 register returns the pin value, regardless of whether the peripheral function uses that pin as its input pin.

However, if the read-modify-write (RMW) type of instruction is used to read the PDR0 register, the PDR0 register value is re-

turned.

Operation at reset

If the CPU is reset, all bits in the DDR0 register are initialized to “0” and port input is enabled. As for a pin shared with analog input,

its port input is disabled because the AIDRL register is initialized to “0”.

Operation in stop mode and watch mode

• If the pin state setting bit in the standby control register (STBC:SPL) is set to “1” and the device transits to stop mode or watch

mode, the pin is compulsorily made to enter the high impedance state regardless of the DDR0 register value. The input of that

pin is locked to “L” level and blocked in order to prevent leaks due to input open. However, if the interrupt input is enabled for

the external interrupt (INT02 to INT07), the input is enabled and not blocked.

• If the pin state setting bit is “0”, the state of the port I/O or that of the peripheral function I/O remains unchanged and the output

level is maintained.

Operation as an analog input pin

• Set the bit in the DDR0 register bit corresponding to the analog input pin to “0” and the bit corresponding to that pin in the AIDRL

• For a pin shared with other peripheral functions, disable the output of such peripheral functions. In addition, set the correspond-

ing bit in the PUL0 register to “0”.

Operation as an external interrupt input pin

• Set the bit in the DDR0 register corresponding to the external interrupt input pin to “0”.

• For a pin shared with other peripheral functions, disable the output of such peripheral functions.

• The pin value is always input to the external interrupt circuit. When using a pin for a function other than the interrupt, disable the

external interrupt function corresponding to that pin.

Operation of the pull-up register

Setting the bit in the PUL0 register to “1” makes the pull-up resistor be internally connected to the pin. When the pin output is “L”

level, the pull-up resistor is disconnected regardless of the value of the PUL0 register.

MB95650L Datasheet(PDF) 35 Page - Cypress Semiconductor

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