mc9s08sg4 Freescale Semiconductor, Inc, mc9s08sg4 Datasheet - Page 77

• Manufacturer Part Number: mc9s08sg4
• Description: 8-bit Microcontroller Family
• Manufacturer: Freescale Semiconductor, Inc

6.4.3
The pin interrupts can be configured to use an internal pull-up/pull-down resistor using the associated I/O
port pull-up enable register. If an internal resistor is enabled, the PTxES register is used to select whether
the resistor is a pull-up (PTxESn = 0) or a pull-down (PTxESn = 1).
6.4.4
When a pin interrupt is first enabled, it is possible to get a false interrupt flag. To prevent a false interrupt
request during pin interrupt initialization, the user should do the following:
6.5
Pin behavior following execution of a STOP instruction depends on the stop mode that is entered. An
explanation of pin behavior for the various stop modes follows:
6.6
This section provides information about the registers associated with the parallel I/O ports. The data and
data direction registers are located in page zero of the memory map. The pull up, slew rate, drive strength,
and interrupt control registers are located in the high page section of the memory map.
Refer to tables in
pin control registers. This section refers to registers and control bits only by their names. A Freescale
Semiconductor-provided equate or header file normally is used to translate these names into the
appropriate absolute addresses.
Freescale Semiconductor
1. Mask interrupts by clearing PTxIE in PTxSC.
2. Select the pin polarity by setting the appropriate PTxESn bits in PTxES.
3. If using internal pull-up/pull-down device, configure the associated pull enable bits in PTxPE.
4. Enable the interrupt pins by setting the appropriate PTxPEn bits in PTxPE.
5. Write to PTxACK in PTxSC to clear any false interrupts.
6. Set PTxIE in PTxSC to enable interrupts.
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Stop2 mode is a partial power-down mode, whereby I/O latches are maintained in their state as
before the STOP instruction was executed. CPU register status and the state of I/O registers should
be saved in RAM before the STOP instruction is executed to place the MCU in stop2 mode. Upon
recovery from stop2 mode, before accessing any I/O, the user should examine the state of the PPDF
bit in the SPMSC2 register. If the PPDF bit is 0, I/O must be initialized as if a power on reset had
occurred. If the PPDF bit is 1, I/O data previously stored in RAM, before the STOP instruction was
executed, peripherals may require being initialized and restored to their pre-stop condition. The
user must then write a 1 to the PPDACK bit in the SPMSC2 register. Access to I/O is now permitted
again in the user application program.
In stop3 mode, all I/O is maintained because internal logic circuity stays powered up. Upon
recovery, normal I/O function is available to the user.
Pin Behavior in Stop Modes
Parallel I/O and Pin Control Registers
Pull-up/Pull-down Resistors
Pin Interrupt Initialization
Chapter 4,
“Memory,” for the absolute address assignments for all parallel I/O and their
MC9S08SG8 MCU Series Data Sheet, Rev. 3
Chapter 6 Parallel Input/Output Control
77