s908qc16vdse Freescale Semiconductor, Inc, s908qc16vdse Datasheet - Page 109

• Manufacturer Part Number: s908qc16vdse
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Figure 11-3
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.
11.3.3 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
PTAPUE[5:0] — Port A Input Pullup Enable Bits
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.
These read/write bits are software programmable to enable pullup devices on port A pins.
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
1 = Corresponding port A pin configured to have internal pull if its DDRA bit is set to 0
0 = Pullup device is disconnected on the corresponding port A pin regardless of the state of its
DDRA bit
— Enable PTA4 on OSC2 Pin
shows the port A I/O logic.
Reset:
Read:
Write:
READ DDRA ($0004)
WRITE DDRA ($0004)
WRITE PTA ($0000)
READ PTA ($0000)
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 4
Figure 11-4. Port A Input Pullup Enable Register (PTAPUE)
OSC2EN
Bit 7
0
= Unimplemented
6
0
RESET
Figure 11-3
Figure 11-3. Port A I/O Circuit
PTAPUE5
5
0
does not apply to PTA2.
PTAPUE4
DDRAx
PTAx
NOTE
4
0
PTAPUE3
3
0
PTAPUE2
2
0
TO KEYBOARD INTERRUPT CIRCUIT
PTAPUEx
PTAPUE1
1
0
PULLUP
PTAPUE0
PTAx
Bit 0
0
Port A
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