Input/Output Ports (PORTS)
MC68HC908QL4 MC68HC908QL3 MC68HC908QL2 Data Sheet, Rev. 4
114
Freescale Semiconductor
PTAPUE[5:0] — Port A Input Pullup/Down Enable Bits
These read/write bits are software programmable to enable pullup/down devices on port A pins.
1 = Corresponding port A pin configured to have internal pullup/down if its DDRA bit is set to 0
0 = Pullup/down device is disconnected on the corresponding port A pin regardless of the state of
its DDRA bit
12.2.4 Port A Summary Table
The following table summarizes the operation of the port A pins when used as a general-purpose
input/output pins.
12.3 Port B
Port B is an 8-bit special function port that shares its pins with the 2-channel timer interface module (TIM)
(see
Chapter 15 Timer Interface Module (TIM)
), the 10-bit ADC (see
Chapter 3 Analog-to-Digital
Converter (ADC10) Module
), and the slave LIN interface controller (SLIC) module (see
Chapter 14 Slave
LIN Interface Controller (SLIC) Module
).
Each port B pin also has a software configurable pullup device if the corresponding port pin is configured
as an input port.
12.3.1 Port B Data Register
The port B data register (PTB) contains a data latch for each of the port B pins.
PTB[7:0] — Port B Data Bits
These read/write bits are software programmable. Data direction of each port B pin is under the control
of the corresponding bit in data direction register B. Reset has no effect on port B data.
Table 12-1. Port A Pin Functions
PTAPUE
Bit
DDRA
Bit
PTA
Bit
I/O Pin
Mode
Accesses to DDRA
Read/Write
Accesses to PTA
Read
Write
1
0
X
(1)
1. X = don’t care
2. I/O pin pulled to V
Pull
(V
DD
or V
SS
) by internal pullup or pulldown.
3. Writing affects data register, but does not affect input.
4. Hi-Z = high impedance
5. Output does not apply to PTA2
Input, V
Pull(2)
DDRA5–DDRA0
Pin
PTA5–PTA0
(3)
0
0
X
Input, Hi-Z
(4)
DDRA5–DDRA0
Pin
PTA5–PTA0
(3)
X
1
X
Output
DDRA5–DDRA0
PTA5–PTA0
PTA5–PTA0
(5)
Bit 7
6
5
4
3
2
1
Bit 0
Read:
PTB7
PTB6
PTB5
PTB4
PTB3
PTB2
PTB1
PTB0
Write:
Reset:
Unaffected by reset
Figure 12-5. Port B Data Register (PTB)