MPC563XM Reference Manual, Rev. 1
1200
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
26.5.8
Continuous Serial Communications Clock
The DSPI provides the option of generating a continuous SCK signal for slave peripherals that require a
continuous clock.
Continuous SCK is enabled by setting the CONT_SCKE bit in the DSPI_MCR. Continuous SCK is valid
in all configurations.
Continuous SCK is only supported for CPHA=1. Setting CPHA=0 will be ignored if the CONT_SCKE bit
is set. Continuous SCK is supported for Modified Transfer Format.
Clock and transfer attributes for the Continuous SCK mode are set according to the following rules:
•
When the DSPI is in SPI configuration, CTAR0 shall be used initially. At the start of each SPI
frame transfer, the CTAR specified by the CTAS for the frame shall be used.
•
When the DSPI is in DSI configuration, the CTAR specified by the DSICTAS field shall be used
at all times.
•
When the DSPI is in CSI configuration, the CTAR selected by the DSICTAS field shall be used
initially. At the start of a SPI frame transfer, the CTAR specified by the CTAS value for the frame
shall be used. At the start of a DSI frame transfer, the CTAR specified by the DSICTAS field shall
be used.
•
In all configurations, the currently selected CTAR shall remain in use until the start of a frame with
a different CTAR specified, or the Continuous SCK mode is terminated.
It is recommended that the baud rate is the same for all transfers made while using the Continuous SCK.
Switching clock polarity between frames while using Continuous SCK can cause errors in the transfer.
Continuous SCK operation is not guaranteed if the DSPI is put into the External Stop Mode or Module
Disable Mode.
Enabling Continuous SCK disables the PCS to SCK delay and the Delay after Transfer (t
DT
) is fixed at
one T
SCK
cycle. When TSB configuration is enabled the t
DT
is programmable to a minimum of 1xT
SCK
cycles by configuring PDT and DT values in the respective CTAR register.
shows timing
diagram for Continuous SCK format with Continuous Selection disabled.
Figure 26-36. Continuous SCK Timing Diagram (CONT=0)
t
DT
SCK
PCS
SCK
Master SOUT
Master SIN
(CPOL = 0)
(CPOL = 1)
Содержание MPC5632M
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