MC908QT1 FREESCALE [Freescale Semiconductor, Inc], MC908QT1 Datasheet - Page 99

• Manufacturer Part Number: MC908QT1
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Figure 12-3
When DDRAx is a 1, reading address $0000 reads the PTAx data latch. When DDRAx is a 0, reading
address $0000 reads the voltage level on the pin. The data latch can always be written, regardless of the
state of its data direction bit.
12.2.3 Port A Input Pullup Enable Register
The port A input pullup enable register (PTAPUE) contains a software configurable pullup device for each
if the six port A pins. Each bit is individually configurable and requires the corresponding data direction
register, DDRAx, to be configured as input. Each pullup device is automatically and dynamically disabled
when its corresponding DDRAx bit is configured as output.
OSC2EN
Freescale Semiconductor
This read/write bit configures the OSC2 pin function when internal oscillator or RC oscillator option is
selected. This bit has no effect for the XTAL or external oscillator options.
1 = OSC2 pin outputs the internal or RC oscillator clock (BUSCLKX4)
0 = OSC2 pin configured for PTA4 I/O, having all the interrupt and pullup functions
— Enable PTA4 on OSC2 Pin
shows the port A I/O logic.
Address: $000B
Reset:
Read:
Write:
Figure 12-4. Port A Input Pullup Enable Register (PTAPUE)
READ DDRA ($0004)
WRITE DDRA ($0004)
WRITE PTA ($0000)
READ PTA ($0000)
OSC2EN
Bit 7
0
= Unimplemented
MC68HC908QY/QT Family Data Sheet, Rev. 5
6
0
Figure 12-3
RESET
Figure 12-3. Port A I/O Circuit
PTAPUE5
5
0
does not apply to PTA2
PTAPUE4
NOTE
DDRAx
PTAx
4
0
PTAPUE3
3
0
PTAPUE2
TO KEYBOARD INTERRUPT CIRCUIT
2
0
PTAPUEx
PTAPUE1
1
0
30 k
PTAPUE0
Bit 0
PTAx
0
Port A
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