S9S08AW16A FREESCALE [Freescale Semiconductor, Inc], S9S08AW16A Datasheet - Page 87

• Manufacturer Part Number: S9S08AW16A
• Description: HCS08 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

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.
When a shared analog function is enabled for a pin, all digital pin functions are disabled. A read of the port
data register returns a value of 0 for any bits which have shared analog functions enabled. In general,
whenever a pin is shared with both an alternate digital function and an analog function, the analog function
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. 8
Q
Q
(S08KBIV1)” for more information about using port G pins as
(S08ICGV4)” for more information about using port G pins
1
0
Synchronizer
Output Enable
Output Data
Chapter 6 Parallel Input/Output
Input Data
87