Datasheet

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SBAS253E − MAY 2003 − REVISED JULY 2006
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3.8.3 Binary Counters and Registers
The complete up/down counter includes two 16-bit counters and five 16-bit shadow registers. The first counter
is a 16-bit up/down counter, which counts upwards or downwards on the EDGE input signal as a function of
the U/D
signal. This is the coarse angle counter, and it is called EDGECNT. For the fine angle computation,
the second 16-bit counter, TIMECOUNT, is implemented. This counter increments with the system clock and
resets when the EDGE signal occurs. The TIMECOUNT counter cannot be decremented. The system is
shown in Figure 1−27 and the timing is shown in Figure 1−28. The U/D
signal is high, counting upwards, when
B1 runs before A1. The U/D
signal is low, counting downwards, when A1 runs before B1. The EDGE signal
is set by every filtered edge of A1 and B1.
16−Bit UP/DN
Binary Counter
U/D
EDGE
UP/DN
CNT
16−Bit
Register
HOLD2
ASEDGCNT
LE
16−Bit
Register
HOLD1
SYEDGCNT
EDGECNT
LE
16−Bit UP/DN
Binary Counter
CLR
CLK
16−Bit
Register
HOLD1
SYEDGPRDEDGEPRDTIMECOUNT
LE
16−Bit
Register
LE
16−Bit
Register
HOLD1
SYEDGTIME
LE
Figure 1−27. Detail Counter Block Diagram