MC68HC08LT8 Datasheet, PDF (98/156 Pages) Freescale Semiconductor, Inc – Microcontrollers

Input/Output (I/O) Ports
9.3 Port B
Port B is an 6-bit special function port that shares four of its port pins with the two timers (TIM1 and TIM2)
and two of its ports pins with the liquid crystal display (LCD) driver module. Port pin, PTB2, is also shared
with the external clock input of the programmable periodic interrupt (PPI) module.
NOTE
PTB6–PTB7 pins are not available on 44-pin package.
9.3.1 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
Read:
0
PTB7
PTB6
Write:
0
PTB3
PTB2
Reset:
Unaffected by reset
Alternative Functions: FP2
FP1
T1CH1 T1CH0
Additional Functions:
PPIECK
High current sink
Figure 9-5. Port B Data Register (PTB)
1
PTB1
T2CH1
Bit 0
PTB0
T2CH0
PTB[7:6, 3:0] — 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.
T1CH[1:0] — Timer 1 Channel I/O Bits
The T1CH1 and T1CH0 pins are the TIM1 input capture/output compare pins. The edge/level select
bits, ELSxB:ELSxA, determine whether the PTB2/T1CH0 and PTB3/T1CH1 pins are timer channel I/O
pins or general-purpose I/O pins. See Chapter 6 Timer Interface Module (TIM).
T2CH[1:0] — Timer 2 Channel I/O Bits
The T2CH1 and T2CH0 pins are the TIM2 input capture/output compare pins. The edge/level select
bits, ELSxB:ELSxA, determine whether the PTB0/T2CH0 and PTB1/T2CH1 pins are timer channel I/O
pins or general-purpose I/O pins. See Chapter 6 Timer Interface Module (TIM).
PPIECK — External Clock Source Input for PPI
The PPIECK pin is the external clock input to the PPI module. It is selected by setting the bits
PPI1CLKS[1:0] = 01 in the port B high current drive control register. See 7.6 PPI1 Status and Control
Register (PPI1SCR).
FP[2:1] — LCD Driver Frontplanes 2–1
FP[2:1] are pins used for the frontplane output of the LCD driver module. The enable bit, LCDE, in the
LCDCR register determine whether the PTB7/FP2–PTB6/FP1 pins are LCD frontplane driver pins or
general-purpose I/O pins. See Chapter 8 Liquid Crystal Display (LCD) Driver.
MC68HC08LT8 Data Sheet, Rev. 1
98
Freescale Semiconductor