mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 890

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

Functional Description
37.4.22.4 Period Measurement
If the channels (n) and (n+1) are configured to capture consecutive edges of the same
polarity, then the period of the channel (n) input signal is measured. If both channels (n)
and (n+1) are configured to capture rising edges (ELS(n)B:ELS(n)A = 0:1 and ELS(n
+1)B:ELS(n+1)A = 0:1), then the period between two consecutive rising edges is
measured. If both channels (n) and (n+1) are configured to capture falling edges
(ELS(n)B:ELS(n)A = 1:0 and ELS(n+1)B:ELS(n+1)A = 1:0), then the period between
two consecutive rising edges is measured.
The period measurement can be made in one-shot capture mode
Mode) or continuous capture mode
The following figure shows an example of the dual edge capture – one-shot mode used to
measure the period between two consecutive rising edges. The DECAPEN bit selects the
dual edge capture mode, so it keeps set in all operation mode. The DECAP bit is set to
890
Figure 37-212. Dual Edge Capture – Continuous Mode for Positive Polarity Pulse Width
Note
- The commands set DECAPEN, set DECAP, clear CH(n)F, and clear CH(n+1)F are made by the user.
channel (n) input
DECAPEN bit
(after the filter
channel input)
CH(n+1)F bit
C(n+1)VH:L
DECAP bit
FTM counter
CH(n)F bit
C(n)VH:L
clear CH(n+1)F
clear CH(n)F
set DECAPEN
set DECAP
1
2
MCF51JF128 Reference Manual, Rev. 2, 03/2011
3
1
2
4
5
3
4
6
(Continuous Capture
5
7
6
Measurement
8
Preliminary
7
8
9
10
11
10
9
12
13
14
11
12
15
Mode).
16
17
16
18
15
19
(One-Shot Capture
20
Freescale Semiconductor, Inc.
19
20
21
22
23
22
21
24
25
23
24
26
27
28