Datasheet

Port B
MC68HC908AP Family Data Sheet, Rev. 4
Freescale Semiconductor 263
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.
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.
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.
Address: $000C
Bit 7654321Bit 0
Read:
LEDA7 LEDA6 LEDA5 LEDA4 LEDA3 LEDA2 LEDA1 LEDA0
Write:
Reset:00000000
Figure 16-5. Port A LED Control Register (LEDA)
Address: $0001
Bit 7654321Bit 0
Read:
PTB7 PTB6 PTB5 PTB4 PTB3 PTB2 PTB1 PTB0
Write:
Reset: Unaffected by reset
Alternative Function: T2CH1 T2CH0 T1CH1 T1CH0 RxD TxD SCL SDA
Figure 16-6. Port B Data Register (PTB)