Datasheet

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SBAS253E − MAY 2003 − REVISED JULY 2006
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57
When EDGECNT cause an over- or under-flow, the corresponding bit in the Interrupt Register is set. The
counter continues to increment or decrement in value. When the EDGE signal rises, the TIMECOUNT value
is latched into the shadow register EDGEPRD. The value of EDGEPRD is the number of system clocks
between two valid edges of the input signals from the comparators. This value is reciprocally proportional to
the angular speed of the position sensor. The value in the EDGEPRD register is latched in the SYEDGPRD
Register on the synchronous hold signal, HOLD1
.
The EDGECNT and TIMECOUNT counter values are stored into the shadow registers (SYEDGCNT and
SYEDGPRD) with the synchronous hold signal, HOLD1
, which samples the analog inputs. The value of the
SYEDGTIME Register represents the time between the last EDGE signal and the synchronous hold signal
HOLD1
. The EDGECNT counter value is stored into a shadow register ASEDGCNT on the asynchronous
sample signal HOLD2
.
The shadow registers SYEDGCNT, ASEDGCNT, SYEDGPRD and SYEDGTIME can be read through the
register map. The counter EDGECNT can be written through the address of the SYEDGCNT Register in the
register map. The 14 MSBs of the written data are stored in the EDGECNT register. The two LSBs are
determined from the inputs FiltA1 and FiltB1; see the Edge Count Register section. This is to prevent
inconsistency between the EDGECNT counters and the ADC data of the position sensor input signals.
FiltB1
FiltA1
EDGE
U/D
EDGECNT N−2 N−1 N N−1 N−2 N−3 N−4 N−5
HOLD1
SYEDGCNT
HOLD2
ASEDGCNT
CLK
TIMECOUNT
EDGEPRD EPNClk EPNClk EPNClk EPNClk
EPNClk
EPTime
EPNClk
EPNClk
EPTime
EPNClk EPNClk EPNClk
SYEDGPRD
SYEDGTIME
N−2
N−4
Figure 1−28. Detail Counter Timing Diagram