Texas Instruments Digital Signal Processor SM320F2812-HT User Manual
Page 104
t
w(PWM)
t
d(PWM)XCO
PWMx
XCLKOUT
(see Note A)
XCLKOUT
(see Note A)
t
w(TDIR)
TDIRx
SGUS062B
–
JUNE 2009
–
REVISED JUNE 2011
Table 6-13. PWM Switching Characteristics
(1) (2)
PARAMETER
TEST CONDITIONS
MIN
MAX
UNIT
t
w(PWM)
(3) (4)
Pulse duration, PWMx output high/low
25
ns
t
d(PWM)XCO
Delay time, XCLKOUT high to PWMx output switching
XCLKOUT = SYSCLKOUT/4
10
ns
(1)
See the GPIO output timing for fall/rise times for PWM pins.
(2)
PWM pin toggling frequency is limited by the GPIO output buffer switching frequency (20 MHz).
(3)
PWM outputs may be 100%, 0%, or increments of t
c(HCO)
with respect to the PWM period.
(4)
Not production tested.
Table 6-14. Timer and Capture Unit Timing Requirements
(1) (2) (3)
MIN
MAX
UNIT
Without input qualifier
2
×
t
c(SCO)
t
w(TDIR)
Pulse duration, TDIRx low/high
cycles
With input qualifier
1
×
t
c(SCO)
+ IQT
(4)
Without input qualifier
2
×
t
c(SCO)
t
w(CAP)
Pulse duration, CAPx input low/high
cycles
With input qualifier
1 x t
c(SCO)
+ IQT
(4)
t
w(TCLKINL)
Pulse duration, TCLKINx low as a percentage of TCLKINx cycle time
40
60
%
t
w(TCLKINH)
Pulse duration, TCLKINx high as a percentage of TCLKINx cycle time
40
60
%
t
c(TCLKIN)
Cycle time, TCLKINx
4
×
t
c(HCO)
ns
(1)
The QUALPRD bit field value can range from 0 (no qualification) through 0xFF (510 SYSCLKOUT cycles). The qualification sampling
period is 2n SYSCLKOUT cycles, where n is the value stored in the QUALPRD bit field. As an example, when QUALPRD = 1, the
qualification sampling period is 1
×
2 = 2 SYSCLKOUT cycles (i.e., the input is sampled every 2 SYSCLKOUT cycles). Six such samples
are taken over five sampling windows, each window being 2n SYSCLKOUT cycles. For QUALPRD = 1, the minimum width that is
needed is 5
×
2 = 10 SYSCLKOUT cycles. However, since the external signal is driven asynchronously, a 11-SYSCLKOUT-wide pulse
ensures reliable recognition.
(2)
Maximum input frequency to the QEP = min[HSPCLK/2, 20 MHz]
(3)
Not production tested.
(4)
Input Qualification Time (IQT) = [5
×
QUALPRD
Ч
2]
Ч
t
c(SCO)
A.
XCLKOUT = SYSCLKOUT
Figure 6-16. PWM Output Timing
A.
XCLKOUT = SYSCLKOUT
Figure 6-17. TDIRx Timing
104
Electrical Specifications
Copyright
©
2009
–
2011, Texas Instruments Incorporated
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