Freescale Semiconductor MC68HC908MR16 ユーザーズマニュアル

I/O Registers

MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1

Freescale Semiconductor

231

TOVx — Toggle-On-Overflow Bit

When channel x is an output compare channel, this read/write bit controls the behavior of the channel
x output when the TIMA counter overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.

1 = Channel x pin toggles on TIMA counter overflow.
0 = Channel x pin does not toggle on TIMA counter overflow.

NOTE

When TOVx is set, a TIMA counter overflow takes precedence over a
channel x output compare if both occur at the same time.

CHxMAX — Channel x Maximum Duty Cycle Bit

When the TOVx is 1 and clear output on compare is selected, setting the CHxMAX bit forces the duty
cycle of buffered and unbuffered PWM signals to 100 percent. As

Figure 16-9

shows, CHxMAX bit

takes effect in the cycle after it is set or cleared. The output stays at 100 percent duty cycle level until
the cycle after CHxMAX is cleared.

Figure 16-9. CHxMAX Latency

Table 16-2. Mode, Edge, and Level Selection

MSxB:MSxA

ELSxB:ELSxA

Mode

Configuration

Output preset

Pin under port control; initialize timer output level high

Pin under port control; initialize timer output level low

Input capture

Capture on rising edge only

Capture on falling edge only

Capture on rising or falling edge

Output

compare

or PWM

Software compare only

Toggle output on compare

Clear output on compare

Set output on compare

Buffered

output compare

or buffered PWM

Toggle output on compare

Clear output on compare

Set output on compare

OUTPUT

OVERFLOW

PTEx/TCHx

PERIOD

CHxMAX

OVERFLOW

COMPARE

OUTPUT

COMPARE

OUTPUT

COMPARE

OUTPUT

COMPARE

TOVx