MC68HC908QL4 Datasheet, PDF (116/226 Pages) Motorola, Inc – Microcontrollers

Input/Output Ports (PORTS)
12.4.3 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.
Bit 7
6
5
4
3
2
1
Bit 0
Read:
PTBPUE7 PTBPUE6 PTBPUE5 PTBPUE4 PTBPUE3 PTBPUE2 PTBPUE2 PTBPUE0
Write:
Reset: 0
0
0
0
0
0
0
0
Figure 12-8. Port B Input Pullup Enable Register (PTBPUE)
PTBPUE[7:0] — Port B Input Pullup Enable Bits
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.
12.4.4 Port B Summary Table
The following table summarizes the operation of the port A pins when used as a general-purpose
input/output pins.
Table 12-2. Port B Pin Functions
DDRB
Bit
0
1
PTB
Bit
X⁽¹⁾
X
I/O Pin
Mode
Input, Hi-Z⁽²⁾
Output
Accesses to DDRB
Read/Write
DDRB7–DDRB0
DDRB7–DDRB0
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect the input.
Accesses to PTB
Read
Write
Pin
PTB7–PTB0⁽³⁾
Pin
PTB7–PTB0
MC68HC908QL4 Data Sheet, Rev. 7
116
Freescale Semiconductor