FXTH870xD
Sensors
Freescale Semiconductor, Inc.
71
9.4.2
Timer Counter Registers (TPM1CNTH:TPM1CNTL)
The two read-only TPM1 counter registers contain the high and low bytes of the value in the TPM1 counter. Reading either byte
(TPM1CNTH or TPM1CNTL) 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 TPM1CNTH or TPM1CNTL, or any write to the timer status/control register (TPM1SC).
Reset clears the TPM1 counter registers.
When BACKGROUND mode is active, the timer counter and the coherency mechanism are frozen such that the buffer latches
remain in the state they were in when the BACKGROUND mode became active even if one or both bytes of the counter are read
while BACKGROUND mode is active.
9.4.3
Timer Counter Modulo Registers (TPM1MODH:TPM1MODL)
The read/write TPM1 modulo registers contain the modulo value for the TPM1 counter. After the TPM1 counter reaches the
modulo value, the TPM1 counter resumes counting from 0x0000 at the next clock (CPWMS = 0) or starts counting down
(CPWMS = 1), and the overflow flag (TOF) becomes set. Writing to TPM1MODH or TPM1MODL inhibits TOF and overflow
interrupts until the other byte is written. Reset sets the TPM1 counter modulo registers to 0x0000, which results in a free-running
timer counter (modulo disabled).
Table 48. Prescale Divisor Selection
PS2:PS1:PS0
TPM1 Clock Source Divided-By
0:0:0
1
0:0:1
2
0:1:0
4
0:1:1
8
1:0:0
16
1:0:1
32
1:1:0
64
1:1:1
128
$0011
7
6
5
4
3
2
1
0
R
Bit 15
14
13
12
11
10
9
Bit 8
W
Any write to TPMCNTH clears the 16-bit counter.
Reset
0
0
0
0
0
0
0
0
Figure 44. Timer Counter Register High (TPM1CNTH)
$0012
7
6
5
4
3
2
1
0
R
Bit 7
6
5
4
3
2
1
Bit 0
W
Any write to TPMCNTL clears the 16-bit counter.
Reset
0
0
0
0
0
0
0
0
Figure 45. Timer Counter Register Low (TPM1CNTL)
$0013
7
6
5
4
3
2
1
0
R
Bit 15
14
13
12
11
10
9
Bit 8
W
Reset
0
0
0
0
0
0
0
0
Figure 46. Timer Counter Modulo Register High (TPM1MODH)
Содержание FXTH870 D Series
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