MC9S08AW32CPUE Datasheet, PDF (171/324 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 10 Timer/Pulse-Width Modulator (S08TPMV2)
Table 10-2. TPM Clock Source Selection
CLKSB:CLKSA
TPM Clock Source to Prescaler Input
0:0
No clock selected (TPMx disabled)
0:1
Bus rate clock (BUSCLK)
1:0
Fixed system clock (XCLK)
1:1
External source (TPMxCLK)^1,2
1 _{The maximum frequency that is allowed as an external clock is one-fourth of the bus}
frequency.
2 _{If the external clock input is shared with channel n and is selected as the TPM clock source,}
the corresponding ELSnB:ELSnA control bits should be set to 0:0 so channel n does not try
to use the same pin for a conflicting function.
Table 10-3. Prescale Divisor Selection
PS2:PS1:PS0
0:0:0
0:0:1
0:1:0
0:1:1
1:0:0
1:0:1
1:1:0
1:1:1
TPM Clock Source Divided-By
1
2
4
8
16
32
64
128
10.4.2 Timer x Counter Registers (TPMxCNTH:TPMxCNTL)
The two read-only TPM counter registers contain the high and low bytes of the value in the TPM counter.
Reading either byte (TPMxCNTH or TPMxCNTL) latches the contents of both bytes into a buffer where
they remain latched until the other byte is read. This allows coherent 16-bit reads in either order. The
coherency mechanism is automatically restarted by an MCU reset, a write of any value to TPMxCNTH or
TPMxCNTL, or any write to the timer status/control register (TPMxSC).
Reset clears the TPM counter registers.
7
6
5
4
3
2
R Bit 15
14
13
12
11
10
1
0
9
Bit 8
W
Any write to TPMxCNTH clears the 16-bit counter.
Reset
0
0
0
0
0
0
0
0
Figure 10-4. Timer x Counter Register High (TPMxCNTH)
MC9S08AW60 Data Sheet, Rev 2
Freescale Semiconductor
171