Advance Information MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
212 Timer Interface A (TIMA) MOTOROLA
Timer Interface A (TIMA)
Setting MS2B links channels 2 and 3 and configures them for buffered
PWM operation. The TIMA channel 2 registers (TACH2H–TACH2L)
initially control the PWM output. TIMA status control register 2 (TASC2)
controls and monitors the PWM signal from the linked channels. MS2B
takes priority over MS2A.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggle s on
TIMA overflows. Subsequent output compares try to force the output to
a state it is already in and have no effect. The result is a 0 percent duty
cycle output.
Setting the channel x maximum duty cycle bit (CHxMAX) and clearing
the TOVx bit generates a 100 percent duty cycle output. (See
11.8.4 TIMA Channel Status and Control Registers.)
11.5 Interrupts
These TIMA sources can generate interrupt requests:
TIMA overflow flag (TOF) — The timer counter value changes on
the falling edge of the internal bus clock. The timer overflow flag
(TOF) bit is set on the falling edge of the internal bus clock
following the timer rollover to $0000. The TIM over flow interrupt
enable bit, TOIE, enables TIM overflow interrupt requests. TOF
and TOIE are in the TIM status and control registers.
TIMA channel flags (CH3F–CH0F) — The CHxF bit is set when an
input capture or output compare occurs on channel x. Channel x
TIMA CPU interrupt requests are controlled by the channel x
interrupt enable bit, CHxIE.
11.6 Wait Mode
The WAIT instruction puts the MCU in low power- co nsu mp ti on stan dby
mode.
The TIMA remains active after the execution of a WAIT instruction. In
wait mode, the TIMA registers are not accessible by the CPU. Any
enabled CPU interrupt request from the TIMA ca n br ing the M CU ou t of
wait mode.