Datasheet
When a rising edge occurs in the channel (n) input signal, the FTM counter value is
captured into channel (n) capture buffer. The channel (n) capture buffer value is
transferred to C(n)VH:L registers when a falling edge occurs in the channel (n) input
signal. C(n)VH:L registers have the FTM counter value when the previous rising edge
occurred, and the channel (n) capture buffer has the FTM counter value when the last
rising edge occurred.
When a negative edge occurs in the channel (n) input signal, the FTM counter value is
captured into channel (n+1) capture buffer. The channel (n+1) capture buffer value is
transferred to C(n+1)VH:L registers when the first byte of C(n)VH:L registers is read.
In the following figure, the read of C(n)VH returns the FTM counter high byte value
when the event 1 occurred, and the read of C(n+1)VL returns the FTM counter low byte
value when the event 1 occurred. The read of C(n+1)VL returns the FTM counter low
byte value when the event 2 occurred, and the read of C(n+1)VH returns the FTM
counter high byte value when the event 2 occurred.
channel (n) input
(after the filter
C(n)VH:L
FTM counter
channel input)
1
C(n+1)VH:L
1
event 1
event 2
event 3
event 4 event 5 event 6 event 7
event 8
event 9
2 3 4 5 6 7 8 9
3 5 7 9
4
3 5 71
2 6 8
2
2
channel (n)
read buffer
1
channel (n+1)
read buffer
channel (n+1)
capture buffer
channel (n)
capture buffer
read C(n)VH
read C(n)VL read C(n+1)VL read C(n+1)VH
Figure 12-258. Dual edge capture mode read coherency mechanism
C(n)VH:L registers must be read prior to C(n+1)VH:L registers in dual edge capture one-
shot and continuous modes for the read coherency mechanism works properly. Either the
high or low bytes of C(n)VH:L and C(n+1)VH:L registers can be accessed first; however,
the C(n)VH:L registers must be read prior to the C(n+1)VH:L registers in dual edge
capture oneshot and continuous modes for the read coherency mechanism to work
properly.
Chapter 12 FlexTimer Module (FTM)
MC9S08PA60 Reference Manual, Rev. 1, 9/2012
Freescale Semiconductor, Inc. 379