mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 893

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

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.
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 high or low bytes of C(n)VH:L and C(n+1)VH:L registers can be accessed at first
that this read coherency mechanism works properly.
Freescale Semiconductor, Inc.
channel (n) input
channel (n+1)
capture buffer
channel (n+1)
capture buffer
channel (n)
read buffer
read buffer
C(n+1)VH:L
channel (n)
(after the filter
channel input)
FTM counter
C(n)VH:L
Figure 37-215. Dual Edge Capture Mode Read Coherency Mechanism
event 1
1
MCF51JF128 Reference Manual, Rev. 2, 03/2011
event 2
1
2
event 3
read C(n)VH
1
3
2
Preliminary
event 4
3
4
read C(n)VL
event 5
3
4
5
event 6
6
5
2
1
read C(n+1)VL
event 7
5
6
7
Chapter 37 FlexTimer (FTM)
event 8
7
8
read C(n+1)VH
2
event 9
9
7
8
9
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