MC68HC908QY4CDW Datasheet, PDF (126/184 Pages) Freescale Semiconductor, Inc – Microcontrollers

Timer Interface Module (TIM)
14.6 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby mode.
The TIM remains active after the execution of a WAIT instruction. In wait mode the TIM registers are not
accessible by the CPU. Any enabled CPU interrupt request from the TIM can bring the MCU out of wait
mode.
If TIM functions are not required during wait mode, reduce power consumption by stopping the TIM before
executing the WAIT instruction.
14.7 TIM During Break Interrupts
A break interrupt stops the TIM counter.
The system integration module (SIM) controls whether status bits in other modules can be cleared during
the break state. The BCFE bit in the break flag control register (BFCR) enables software to clear status
bits during the break state. See 13.8.2 Break Flag Control Register.
To allow software to clear status bits during a break interrupt, write a 1 to the BCFE bit. If a status bit is
cleared during the break state, it remains cleared when the MCU exits the break state.
To protect status bits during the break state, write a 0 to the BCFE bit. With BCFE at 0 (its default state),
software can read and write I/O registers during the break state without affecting status bits. Some status
bits have a two-step read/write clearing procedure. If software does the first step on such a bit before the
break, the bit cannot change during the break state as long as BCFE is at 0. After the break, doing the
second step clears the status bit.
14.8 Input/Output Signals
Port A shares three of its pins with the TIM. Two TIM channel I/O pins are PTA0/TCH0 and PTA1/TCH1
and an alternate clock source is PTA2/TCLK.
14.8.1 TIM Clock Pin (PTA2/TCLK)
PTA2/TCLK is an external clock input that can be the clock source for the TIM counter instead of the
prescaled internal bus clock. Select the PTA2/TCLK input by writing 1s to the three prescaler select bits,
PS[2–0]. (See 14.9.1 TIM Status and Control Register.) When the PTA2/TCLK pin is the TIM clock input,
it is an input regardless of port pin initialization.
14.8.2 TIM Channel I/O Pins (PTA0/TCH0 and PTA1/TCH1)
Each channel I/O pin is programmable independently as an input capture pin or an output compare pin.
PTA0/TCH0 can be configured as a buffered output compare or buffered PWM pin.
14.9 Input/Output Registers
The following I/O registers control and monitor operation of the TIM:
• TIM status and control register (TSC)
• TIM counter registers (TCNTH:TCNTL)
• TIM counter modulo registers (TMODH:TMODL)
• TIM channel status and control registers (TSC0 and TSC1)
• TIM channel registers (TCH0H:TCH0L and TCH1H:TCH1L)
MC68HC908QY/QT Family Data Sheet, Rev. 6
126
Freescale Semiconductor