Deserial Serial Peripheral Interface (DSPI)
25-48
Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
25.4.6.5
Peripheral Chip Select Strobe Enable (PCSS)
The PCSS signal provides a delay to allow the PCS signals to settle after a transition occurs thereby
avoiding glitches. When the DSPI is in Master Mode and PCSSE bit is set in the DSPI_MCR, PCSS
provides a signal for an external demultiplexer to decode the PCS[0] -PCS[4] and PCS[6] -PCS[7] signals
into as many as 128 glitch-free PCS signals.
shows the timing of the PCSS signal relative to
PCS signals.
Figure 25-28. Peripheral Chip Select Strobe Timing
The delay between the assertion of the PCS signals and the assertion of PCSS is selected by the PCSSCK
field in the DSPI_CTAR based on the following formula:
Eqn. 25-5
At the end of the transfer the delay between PCSS negation and PCS negation is selected by the PASC field
in the DSPI_CTAR based on the following formula:
Eqn. 25-6
shows an example of how to compute the t
pcssck
delay.
shows an example of how to compute the t
pasc
delay.
The PCSS signal is not supported when Continuous Serial Communication SCK is enabled
(CONT_SCKE=1).
NOTES:
1
Some values are not reachable (i. e. 9, 11, 13, 15, 17, 18, 19...), to
calculate these values, please see the
2
The values in this row were rounded to the next integer value
Table 25-33. Peripheral Chip Select Strobe Assert Computation Example
PCSSCK
Prescaler
f
periph
Delay before Transfer
0b11
7
100 MHz
70.0 ns
Table 25-34. Peripheral Chip Select Strobe Negate Computation Example
PASC
Prescaler
f
periph
Delay after Transfer
0b11
7
100 MHz
70.0 ns
t
PCSSCK
PCSS
PCSx
t
PASC
t
PCSSCK
1
f
periph
--------------
PCSSCK
=
t
PASC
1
f
periph
--------------
PASC
=
Summary of Contents for PXR4030
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