CHAPTER 7 TIMER/COUNTER FUNCTION
User’s Manual U13850EJ4V0UM
192
(2) Measurement of two pulse widths with free-running counter
The pulse widths of the two signals respectively input to the TIn0 and TIn1 pins can be measured when 16-bit
timer register n (TMn) is used as a free-running counter (refer to
Figure 7-16
).
When the edge specified by bits 4 and 5 (ESn00 and ESn01) of prescaler mode register n0 (PRMn0) is input to
the TIn0 pin, the value of the TMn is loaded to 16-bit capture/compare register n1 (CRn1) and an external
interrupt request signal (INTTMn1) is set.
When the edge specified by bits 6 and 7 (ESn10 and ESn11) in PRMn0 is input to the TIn1 pin, the value of TMn
is loaded to 16-bit capture/compare register n0 (CRn0), and an external interrupt request signal (INTTMn0) is set.
The edges of the TIn0 and TIn1 pins are specified by bits 4 and 5 (ESn00 and ESn01) and bits 6 and 7 (ESn10
and ESn11) of PRMn0, respectively. The rising, falling, or both rising and falling edges can be specified.
The valid edge is detected through sampling at a count clock cycle selected by prescaler mode register n0, n1
(PRMn0, PRMn1), and the capture operation is not performed until the valid level is detected two times.
Therefore, noise with a short pulse width can be removed.
Figure 7-16. Control Register Settings for Measurement of Two Pulse Widths with Free-Running Counter
(a) 16-bit timer mode control registers 0, 1 (TMC0, TMC1)
TMCn3
TMCn2
TMCn1
OVFn
TMCn
0
0
0
0
0
1
0/1
0
Free-running mode
(b) Capture/compare control registers 0, 1 (CRC0, CRC1)
CRCn2
CRCn1
CRCn0
CRCn
0
0
0
0
0
1
0
1
CRn0 as capture
register
Captures valid edge of
TIn1 pin to CRn0.
CRn1 as capture
register
Remark
0/1: When these bits are reset to 0 or set to 1, other functions can be used along with the pulse
width measurement function. For details, refer to
7.1.4 Timer 0, 1 control registers
.
Содержание MPD703030A
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