ADLINK Technology USB-2401, Руководство пользователя

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44 Operation
the counter value in Edge Separation Measurement mode is
shown.
Figure 3-19: Mode 9-Edge Separation Measurement
Mode 10: PWM Output
The USB-1900 Series timer/counter can also simulate a PWM
(Pulse Width Modulation) output. By setting a varying amount
of Pulse_initial_cnt and Pulse_length_cnt, varying pulse fre-
quencies (Fpwm) and duty cycles (Dutypwm) can be obtained.
PWM output is shown.
Figure 3-20: Mode 10-PWM Output
Calculation of the PWM frequency and duty cycle is as follows.
1 3 1 3 1 2 1 1 9 8 7 6
S o f t w a r e s t a r t
5 4 3 2 1 1 1 1 1 1
G a t e
C L K
A U X
C o u n t v a l u e
1 0
T I M E B A S E
P W M O U T
P u l s e _ I n i t i a l _ c n t = 0 x 7 P u l s e _ I e n g t h _ c n t = 0 x B
cnt length Pulse cnt initial Pulse
cnt length Pulse
Duty
cnt length Pulse cnt initial Pulse
F
F
PWM
Tim ebase
PWM
_ _ _ _
_ _
_ _ _ _
+
=
+
=