s908qc16vdse Freescale Semiconductor, Inc, s908qc16vdse Datasheet - Page 111

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

When DDRBx is a 1, reading address $0001 reads the PTBx data latch. When DDRBx is a 0, reading
address $0001 reads the voltage level on the pin. The data latch can always be written, regardless of the
state of its data direction bit.
11.4.3 Port B Input Pullup Enable Register
The port B input pullup enable register (PTBPUE) contains a software configurable pullup device for each
of the eight port B pins. Each bit is individually configurable and requires the corresponding data direction
register, DDRBx, be configured as input. Each pullup device is automatically and dynamically disabled
when its corresponding DDRBx bit is configured as output.
PTBPUE[7:0] — Port B Input Pullup Enable Bits
Freescale Semiconductor
Table 11-2
These read/write bits are software programmable to enable pullup devices on port B pins
1 = Corresponding port B pin configured to have internal pull if its DDRB bit is set to 0
0 = Pullup device is disconnected on the corresponding port B pin regardless of the state of its
DDRB bit.
summarizes the operation of the port B pins.
Reset:
Read:
Write:
Avoid glitches on port B pins by writing to the port B data register before
changing data direction register B bits from 0 to 1.
port B I/O logic.
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 4
PTBPUE7
READ DDRB ($0005)
WRITE DDRB ($0005)
WRITE PTB ($0001)
READ PTB ($0001)
Figure 11-8. Port B Input Pullup Enable Register (PTBPUE)
Bit 7
0
PTBPUE6
6
0
RESET
Figure 11-7. Port B I/O Circuit
PTBPUE5
5
0
PTBPUE4
DDRBx
NOTE
PTBx
4
0
PTBPUE3
3
0
PTBPUE2
Figure 11-7
2
0
PTBPUEx
PTBPUE2
1
0
shows the
PULLUP
PTBPUE0
Bit 0
PTBx
0
Port B
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