mcf51ac256a Freescale Semiconductor, Inc, mcf51ac256a Datasheet - Page 231

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

Freescale Semiconductor
CPWMS = 0 (FTM counting is up)
FTMxCNTINH:L = 0x0000
FTMxMODH:L = 0x0004
FTM counter
period of FTM counter clock
Figure 11-28. Example of FTM up counting with FTMxCNTINH:FTMxCNTINL = 0x0000
FTM operation is only valid when the value of the
FTMxCNTINH:FTMxCNTINL registers is less than the value of the
FTMxMODH:FTMxMODL registers (either in the unsigned counting or
signed counting). It is the responsibility of the software to ensure that the
values in the FTMxCNTINH:FTMxCNTINL and
FTMxMODH:FTMxMODL registers meet this requirement. Any values of
FTMxCNTINH:FTMxCNTINL and FTMxMODH:FTMxMODL that do
not satisfy this criteria can result in unpredictable behavior.
FTMxMODH:FTMxMODL = FTMxCNTINH:FTMxCNTINL is a
redundant condition. In this case, the FTM counter is always equal to
FTMxMODH:FTMxMODL and the TOF bit will be set in each rising edge
of the FTM counter clock.
When FTMxMODH:FTMxMODL = 0x0000 and
FTMxCNTINH:FTMxCNTINL = 0x0000 (for example after reset) and
FTMEN = 1, the FTM counter remains stopped at 0x0000 until a non-zero
value is written into the FTMxMODH:FTMxMODL or
FTMxCNTINH:FTMxCNTINL registers.
Setting FTMxCNTINH:L to be greater than the value of FTMxMODH:L is
not recommended as this unusual setting may make the FTM operation
difficult for users to comprehend. There is no restriction on this
configuration however, and an example is shown in
3
period of counting = (FTMxMODH:L - FTMxCNTINH:L + 0x0001) x period of FTM counter clock
MCF51AC256 ColdFire Integrated Microcontroller Reference Manual, Rev. 5
4
0
= (FTMxMODH:L + 0x0001) x period of FTM counter clock
1
2
3
NOTE
4
0
1
Figure
2
11-29.
3
4
FlexTimer Module (FTMV1)
0
1
2
11-31