NXP Semiconductors MC9S08QL4, Reference Manual

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Timer/Pulse-Width Modulator (S08TPMV3)
MC9S08QL8 MCU Series Reference Manual, Rev. 1
NXP Semiconductors 223
15.6.2.1 Timer Overflow Interrupt (TOF) Description
The meaning and details of operation for TOF interrupts varies slightly depending upon the mode of
operation of the TPM system (general purpose timing functions versus center-aligned PWM operation).
The flag is cleared by the two step sequence described above.
15.6.2.1.1 Normal Case
When CPWMS is cleared, TOF is set when the timer counter changes from the terminal count (the value
in the modulo register) to 0x0000. If the TPM counter is a free-running counter, the update is made when
the TPM counter changes from 0xFFFF to 0x0000.
15.6.2.1.2 Center-Aligned PWM Case
When CPWMS is set, TOF is set when the timer counter changes direction from up-counting to
down-counting at the end of the terminal count (the value in the modulo register).
15.6.2.2 Channel Event Interrupt Description
The meaning of channel interrupts depends on the channel’s current mode (input capture, output compare,
edge-aligned PWM, or center-aligned PWM).
15.6.2.2.1 Input Capture Events
When a channel is configured as an input capture channel, the ELSnB:ELSnA bits select if channel pin is
not controlled by TPM, rising edges, falling edges, or any edge as the edge that triggers an input capture
event. When the selected edge is detected, the interrupt flag is set. The flag is cleared by the two-step
sequence described in
Section 15.6.2, Description of Interrupt Operation .
15.6.2.2.2 Output Compare Events
When a channel is configured as an output compare channel, the interrupt flag is set each time the main
timer counter matches the 16-bit value in the channel value register. The flag is cleared by the two-step
sequence described in
Section 15.6.2, Description of Interrupt Operation .”
15.6.2.2.3 PWM End-of-Duty-Cycle Events
When the channel is configured for edge-aligned PWM, the channel flag is set when the timer counter
matches the channel value register that marks the end of the active duty cycle period. When the channel is
configured for center-aligned PWM, the timer count matches the channel value register twice during each
PWM cycle. In this CPWM case, the channel flag is set at the start and at the end of the active duty cycle
period when the timer counter matches the channel value register. The flag is cleared by the two-step
sequence described in
Section 15.6.2, Description of Interrupt Operation .