mcf51ac256a Freescale Semiconductor, Inc, mcf51ac256a Datasheet - Page 230

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

FlexTimer Module (FTMV1)
11.4.3.1
Up counting is selected when CPWMS = 0.
FTMxCNTINH:FTMxCNTINL defines the starting value of the count and FTMxMODH:FTMxMODL
defines the final value of the count
into the FTM counter, and the counter incremented until the value of FTMxMODH:FTMxMODL is
reached, at which point the counter is reloaded with the contents of FTMxCNTINH:FTMxCNTINL.
The FTM period when using up counting is (FTMxMODH:FTMxMODL -
FTMxCNTINH:FTMxCNTINL + 0x0001) x period of the FTM counter clock.
The TOF bit is set when the FTM counter changes from FTMxMODH:FTMxMODL to
FTMxCNTINH:FTMxCNTINL.
If (FTMxCNTINH:FTMxCNTINL = 0x0000), the FTM counting is equivalent to TPM up counting (that
is, up and unsigned counting)
counter is a negative number in two’s complement, so the FTM counting is up and signed. Conversely if
(FTMxCNTINH[7] = 0 and FTMxCNTINH:L not = 0x0000), then the initial value of the FTM counter is
a positive number, so the FTM counting is up and unsigned.
11-30
FTM counter (in decimal values)
period of FTM counter clock
CPWMS = 0 (FTM counting is up)
FTMxCNTINH:L = 0xFFFC (in two’s complement is equal to -4)
FTMxMODH:L = 0x0004
Up counting
period of counting = (FTMxMODH:L - FTMxCNTINH:L + 0x0001) x period of FTM counter clock
MCF51AC256 ColdFire Integrated Microcontroller Reference Manual, Rev. 5
Figure 11-27. Example of FTM up and signed counting
(Figure
4
-4 -3
(Figure
11-28). If (FTMxCNTINH[7] = 1), then the initial value of the FTM
-2 -1
11-27). The value of FTMxCNTINH:FTMxCNTINL is loaded
0
1
2
3
4
-4
-3
-2
-1 0
1
2
3 4
Freescale Semiconductor
-4 -3