MC9S08DN60 Datasheet, PDF (82/354 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 6 Parallel Input/Output Control
6.3.3 Pull-up/Pull-down Resistors
The port interrupt pins 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).
6.3.4 Pin Interrupt Initialization
When an interrupt pin 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:
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 PTxPSn bits in PTxPS.
5. Write to PTxACK in PTxSC to clear any false interrupts.
6. Set PTxIE in PTxSC to enable interrupts.
6.4 Pin Behavior in Stop Modes
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:
• 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, peripherals may require initialization to be restored to their pre-stop
condition. This can be done using data previously stored in RAM if it was saved before the STOP
instruction was executed. 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.
6.5 Parallel I/O and Pin Control Registers
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 Chapter 4, “Memory,” for the absolute address assignments for all parallel I/O and their
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.
MC9S08DN60 Series Data Sheet, Rev 2
82
Freescale Semiconductor