Port B
16.2.3 Port-A LED Control Register (LEDA)
The port-A LED control register (LEDA) controls the direct LED drive capability on PTA7–PTA0 pins. Each
bit is individually configurable and requires that the data direction register, DDRA, bit be configured as an
output.
Address:
$000C
Bit 7
6
LEDA6
0
5
LEDA5
0
4
LEDA4
0
3
LEDA3
0
2
LEDA2
0
1
LEDA1
0
Bit 0
LEDA0
0
Read:
Write:
Reset:
LEDA7
0
Figure 16-5. Port A LED Control Register (LEDA)
LEDA[7:0] — Port A LED Drive Enable Bits
These read/write bits are software programmable to enable the direct LED drive on an output port pin.
1 = Corresponding port A pin is configured for direct LED drive,
with 15mA current sinking capability
0 = Corresponding port A pin is configured for standard drive
16.3 Port B
Port B is an 8-bit special-function port that shares two of its pins with the multi-master IIC (MMIIC) module,
two of its pins with SCI module, and four of its pins with two timer interface (TIM1 and TIM2) modules.
NOTE
PTB3–PTB0 are open-drain pins when configured as outputs regardless
whether the pins are used as general purpose I/O pins, MMIIC pins, or SCI
pins. Therefore, when configured as general purpose output pins, MMIIC
pins, or SCI pins (the TxD pin), pullup resistors must be connected to these
pins.
16.3.1 Port B Data Register (PTB)
The port B data register contains a data latch for each of the eight port B pins.
Address:
$0001
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
PTB7
PTB6
PTB5
PTB4
PTB3
PTB2
PTB1
PTB0
Unaffected by reset
T1CH0 RxD
Alternative Function: T2CH1
T2CH0
T1CH1
TxD
SCL
SDA
Figure 16-6. Port B Data Register (PTB)
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.
MC68HC908AP Family Data Sheet, Rev. 4
Freescale Semiconductor
263
FREESCALE [ Freescale ]
