TC1796
Peripheral Units (Vol. 2 of 2)
General Purpose Timer Array (GPTA)
User’s Manual 24-82 V2.0, 2007-07
GPTA, V2.0
Figure 24-55 shows an PCM example for an effective period of 6 clocks.
Figure 24-55 Pulse Count Modulation Example 1
Table 24-5 shows the rounding behavior for a period of 100 clocks.
The output is OFF for the remaining cycles of the period. The worst case error is
approximately +2/-1 ON pulses. A subtraction performed via software may be used to
reduce the worst case error.
If the duty cycle is changed at an arbitrary time, the actual duty cycle for the entire current
period will reflect the old duty cycle, the new one, or a mixture of both.
Table 24-5 Implicit PCM Rounding
Desired Duty Cycle Expected ON Pulses Actual ON Pulses
0.000 = 0000 0 0
0.100 = 199A
H
10 11
0.500 = 8000
H
50 50
0.800 = CCCD
H
80 82
0.900 = E666
H
90 90
0.999 = FFBE
H
100 99
1.000 = FFFF
H
100 100
MCT05964
0000
H
0000
H
Timer Value
Normal/
Reversed
0001
H
8000
H
0002
H
4000
H
0003
H
C000
H
0004
H
2000
H
FFFF
H
FFFF
H
Desired
Duty Cycle
0.25 = 4000
H
0.00 = 0000
H
0.50 = 8000
H
0.75 = C000
H
1.00 = FFFF
H
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