MC9S08AC60 Datasheet, PDF (277/348 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 15 Timer/PWM Module (S08TPMV3)
15.8.2.1.2 Center-Aligned PWM Case
When CPWMS=1, TOF gets 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). In this case the TOF
corresponds to the end of a PWM period.
15.8.2.2 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).
15.8.2.2.1 Input Capture Events
When a channel is configured as an input capture channel, the ELSnB:ELSnA control bits select no edge
(off), rising edges, falling edges or any edge as the edge which 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 15.8.2, “Description of Interrupt Operation.”
15.8.2.2.2 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 Section 15.8.2, “Description of Interrupt Operation.”
15.8.2.2.3 PWM End-of-Duty-Cycle Events
For channels configured for PWM operation there are two possibilities. When the channel is configured
for edge-aligned PWM, the channel flag gets set when the timer counter matches the channel value register
which 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 which are the times
when the timer counter matches the channel value register. The flag is cleared by the two-step sequence
described Section 15.8.2, “Description of Interrupt Operation.”
15.9 The Differences from TPM v2 to TPM v3
1. Write to TPMxCnTH:L registers (Section 15.5.2, “TPM-Counter Registers
(TPMxCNTH:TPMxCNTL)) [SE110-TPM case 7]
Any write to TPMxCNTH or TPMxCNTL registers in TPM v3 clears the TPM counter
(TPMxCNTH:L) and the prescaler counter. Instead, in the TPM v2 only the TPM counter is cleared
in this case.
2. Read of TPMxCNTH:L registers (Section 15.5.2, “TPM-Counter Registers
(TPMxCNTH:TPMxCNTL))
— In TPM v3, any read of TPMxCNTH:L registers during BDM mode returns the value of the
TPM counter that is frozen. In TPM v2, if only one byte of the TPMxCNTH:L registers was
read before the BDM mode became active, then any read of TPMxCNTH:L registers during
MC9S08AC60 Series Data Sheet, Rev. 2
Freescale Semiconductor
277