DMA Serial Peripheral Interface (DSPI)
Freescale Semiconductor
31-27
shows an example of the computed delay after transfer.
31.4.3.5
Peripheral Chip Select Strobe Enable (PCSS)
DSPI_PCSS signal provides a delay to allow DSPI_PCS
n
signals to settle after transitioning, which avoids
glitches. When DSPI is in master mode and DSPI_MCR[PCSSE] bit is set, DSPI_PCSS provides a signal
for an external demultiplexer to decode the DSPI_PCS[0:3] signals into as many as 16 glitch-free PCS
signals.
shows the timing of the DSPI_PCSS signal relative to DSPI_PCS
n
signals.
Figure 31-14. Peripheral Chip Select Strobe Timing
The delay between assertion of DSPI_PCS
n
signals and assertion of DSPI_PCSS is selected by the
DSPI_CTAR
n
[PCSSCK] field based on the following:
Eqn. 31-5
At the end of transfer, delay between DSPI_PCSS negation and DSPI_PCS
n
negation is selected by the
DSPI_CTAR
n
[PASC] field based on the following:
Eqn. 31-6
shows an example of the computed t
PCSSCK
delay.
shows an example of the computed t
PASC
delay
.
Table 31-16. Delay after Transfer Computation Example
PDT
Prescaler
Value
DT
Scaler
Value
f
SYS/2
Delay after Transfer
01
3
1110
32768
100 MHz
0.98 ms
Table 31-17. Peripheral Chip Select Strobe Assert Computation Example
PCSSCK
Prescaler
f
SYS/2
Delay before Transfer
0b11
7
100 MHz
70.0 ns
Table 31-18. Peripheral Chip Select Strobe Negate Computation Example
PASC
Prescaler
f
SYS/2
Delay after Transfer
0b11
7
100 MHz
70.0 ns
DSPI_PCSS
DSPI_PCS
n
t
PCSSCK
t
PASC
t
PCSSCK
1
f
SYS/2
-------------
PCSSCK
=
t
PASC
1
f
SYS/2
-------------
PASC
=
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...