mcf51ac256a Freescale Semiconductor, Inc, mcf51ac256a Datasheet - Page 233

• Manufacturer Part Number: mcf51ac256a
• Description: Mcf51ac Flexis
• Manufacturer: Freescale Semiconductor, Inc

11.4.3.3
If (FTMEN = 0) and (FTMxMODH:FTMxMODL = 0x0000 or FTMxMODH:FTMxMODL = 0xFFFF),
the FTM counter is a free running counter. In this case the FTM counter runs free from 0x0000 through
0xFFFF and the TOF bit is set when the FTM counter changes from 0xFFFF to 0x0000
If (FTMEN = 1) and (CPWMS = 0) and (FTMxCNTINH:FTMxCNTINL = 0x0000) and
(FTMxMODH:FTMxMODL = 0xFFFF), the FTM counter is a free running counter. In this case the FTM
Freescale Semiconductor
CPWMS = 1 (FTM counting is up-down)
FTMxCNTINH:L = 0x0000
FTMxMODH:L = 0x0004
period of FTM counter clock
FTM is compatible with TPM module (FTMEN = 0)
FTMxMODH:L = 0x0000
Figure 11-30. Example of up-down counting when FTMxCNTINH:FTMxCNTINL = 0x0000
FTM counter
FTM counter
Free running counter
TOF bit
The up-down counting is only available when (FTMEN = 0) and
(FTMxCNTINH:FTMxCNTINL = 0x0000). The configuration with
(FTMEN = 1) or (FTMxCNTINH:FTMxCNTINL not = 0x0000) when
(CPWMS = 1) is not recommended and its results are not guaranteed.
MCF51AC256 ColdFire Integrated Microcontroller Reference Manual, Rev. 5
...
Figure 11-31. Example when the FTM counter is a free running
0x0003 0x0004 ... 0xFFFE 0xFFFF 0x0000 0x0001 0x0002 0x0003
0
period of counting = 2 x (FTMxMODH:L - FTMxCNTINH:L) x period of FTM counter clock
1
previous value
2
3
4
= 2 x FTMxMODH:L x period of FTM counter clock
3
2
1
set TOF bit
NOTE
0
1
2
3
4
3
2
1
0
0x0004 0x0005 0x0006 ...
1 2
3
FlexTimer Module (FTMV1)
4
(Figure
11-31).
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