mc9s08ac16 Freescale Semiconductor, Inc, mc9s08ac16 Datasheet - Page 87

• Manufacturer Part Number: mc9s08ac16
• Description: Hcs08 Microcontrollers 8-bit Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

the external oscillator is enabled, PTG5 and PTG6 function as oscillator pins. In this case the associated
parallel I/O and pin control registers have no control of the pins.
Refer to
as XTAL and EXTAL pins.
Refer to
keyboard inputs.
6.4
Reading and writing of parallel I/O is done through the port data registers. The direction, input or output,
is controlled through the port data direction registers. The parallel I/O port function for an individual pin
is illustrated in the block diagram below.
The data direction control bits determine whether the pin output driver is enabled, and they control what
is read for port data register reads. Each port pin has a data direction register bit. When PTxDDn = 0, the
corresponding pin is an input and reads of PTxD return the pin value. When PTxDDn = 1, the
corresponding pin is an output and reads of PTxD return the last value written to the port data register.
When a peripheral module or system function is in control of a port pin, the data direction register bit still
controls what is returned for reads of the port data register, even though the peripheral system has
overriding control of the actual pin direction.
Freescale Semiconductor
Chapter 8, “Internal Clock Generator
Chapter 9, “Keyboard Interrupt
Parallel I/O Control
Port Read
BUSCLK
Data
PTxDDn
D
D
PTxDn
Figure 6-9. Parallel I/O Block Diagram
MC9S08AC16 Series Data Sheet, Rev. 0
Q
Q
(S08KBIV1)” for more information about using port G pins as
(S08ICGV4)” for more information about using port G pins
PRELIMINARY
1
0
Synchronizer
Output Enable
Output Data
Chapter 6 Parallel Input/Output
Input Data
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