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CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
Digital Blocks
Figure 17-19. PWM Width Equal to Dead Band Period
In the case where the dead band period is greater than the
high or low of the PWM reference, the output of the associ-
ated phase will not be asserted high.
17.3.3.2
Kill Operation
It is assumed that the KILL input will not be synchronized at
the row input. (This is not a requirement; however, if syn-
chronized, the KILL operation will have up to two 24 MHz
clock cycles latency which is undesirable.) To support the
restart modes, the negation of KILL is internally (in the
block) synchronized to the 24 MHz system clock.
There are three KILL modes supported. In all cases, the
KILL signal asynchronously forces the outputs to logic 0.
The differences in the modes come from how dead band
processing is restarted.
1.
Synchronous Restart Mode
: When KILL is asserted
high, the internal state is held in reset and the initial dead
band period is reloaded into the counter. While KILL is
held high, incoming PWM reference edges are ignored.
When KILL is negated, the next incoming PWM refer-
ence edge restarts dead band processing. See
2.
Asynchronous Restart Mode
: When KILL is asserted
high, the internal state is not affected. When KILL is
negated, the outputs are restored, subject to a minimum
disable time between one-half and one and one-half
clock cycle. See
.
3.
Disable Mode
: There is no specific timing associated
with Disable mode. The block is disabled and the user
must re-enable the function in firmware to continue pro-
cessing.
Figure 17-20. Synchronous Restart KILL Mode
Figure 17-21. Asynchronous Restart Kill Mode
CLK
PWM
PHI1
PHI2
2
2
2
PWM
REFERENCE
PHI2
PHI1
KILL
Short KILL, outputs off for
remainder of current cycle.
Operation resumes on
the next PWM edge.
PWM
REFERENCE
PHI2
PHI1
KILL
Output is off for duration
of KILL on time.
These edges
are skipped.
Operation resumes
on this edge.
PWM
REFERENCE
PHI2
PHI1
KILL
Outputs are forced low only as
long as the KILL is asserted,
subject to the minimum disable
time. Internal operation is
unaffected.
PWM
REFERENCE
PHI2
PHI1
KILL
Outputs are disabled
immediately on KILL.
Minimum disable time
is between ½ and 1½
block clock cycle.
PHI1 or PHI2
KILL
BLOCK CLK
Example of KILL shorter
than the minimum.
Example of KILL longer
than the minimum.
Summary of Contents for CY8C28 series
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