sc9s08mz16 Freescale Semiconductor, Inc, sc9s08mz16 Datasheet - Page 29

• Manufacturer Part Number: sc9s08mz16
• Description: Hcs08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

2.3.7
The remaining pins are shared among general-purpose I/O and on-chip peripheral functions such as timers
and serial I/O systems. Immediately after reset, all of these pins are configured as high-impedance
general-purpose inputs with internal pullup devices disabled.
For information about controlling these pins as general-purpose I/O pins, see
Input/Output.” For information about how and when on-chip peripheral systems use these pins, refer to the
appropriate chapter from
When an on-chip peripheral system is controlling a pin, data direction control bits still determine what is
read from port data registers even though the peripheral module controls the pin direction by controlling
the enable for the pin’s output buffer. See the
Pullup enable bits for each input pin control whether on-chip pullup devices are enabled whenever the pin
is acting as an input even if it is being controlled by an on-chip peripheral module. When IRQ is configured
as the IRQ input and is set to detect rising edges, the pullup enable control bit enables a pulldown device
rather than a pullup device.
Freescale Semiconductor
General-Purpose I/O and Peripheral Ports
To avoid extra current drain from floating input pins, the reset initialization
routine in the application program should either enable on-chip pullup
devices or change the direction of unused pins to outputs so the pins do not
float.
When an alternate function is first enabled, a spurious edge to a module can
occur. To avoid this, clear any associated flags before interrupts are enabled.
Table 2-1
highest priority module will have control over the pin. Selecting a higher
priority pin function with a lower priority function already enabled can
cause spurious edges to the lower priority module. It is recommended that
all modules that share a pin be disabled before enabling another module.
illustrates the priority if multiple modules are enabled. The
Table
2-2.
SC9S08MZ16 MCU Data Sheet, Rev. 0 Draft C
Chapter 6, “Parallel
NOTE
NOTE
Input/Output” chapter for more details.
Chapter 6, “Parallel
Chapter 2 Pins and Connections
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