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Deserial – Serial Peripheral Interface (DSPI)
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
30-51
Switching CTAR registers or changing which PCS signals are asserted between frames while using
continuous selection can cause errors in the transfer. The PCS signal should be negated before CTAR is
switched or different PCS signals are selected.
30.4.8.6
Clock Polarity Switching Between DSPI Transfers
If it is desired to switch polarity between non-continuous DSPI frames, the edge generated by the change
in the idle state of the clock occurs one system clock before the assertion of the chip select for the next
frame. In
, time A shows the one clock interval. Time B is user programmable from a
minimum of two system clocks. Refer to
Section 30.3.2.3, DSPI Clock and Transfer Attributes Registers
Figure 30-35. Polarity Switching Between Frames
30.4.9
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 is 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.
PCS
System Clock
SCK
Frame 1
Frame 0
CPOL = 0
CPOL = 1
A
B
Summary of Contents for PXN2020
Page 1: ...PXN20 Microcontroller Reference Manual Devices Supported PXN2020 PXN2120 PXN20RM Rev 1 06 2011...
Page 42: ...PXN20 Microcontroller Reference Manual Rev 1 lxiv Freescale Semiconductor...
Page 64: ...Introduction PXN20 Microcontroller Reference Manual Rev 1 1 22 Freescale Semiconductor...
Page 112: ...Signal Description PXN20 Microcontroller Reference Manual Rev 1 3 44 Freescale Semiconductor...
Page 118: ...Resets PXN20 Microcontroller Reference Manual Rev 1 4 6 Freescale Semiconductor...
Page 372: ...e200z6 Core Z6 PXN20 Microcontroller Reference Manual Rev 1 13 8 Freescale Semiconductor...
Page 412: ...e200z0 Core Z0 PXN20 Microcontroller Reference Manual Rev 1 14 14 Freescale Semiconductor...
Page 821: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 27 49...
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Page 1376: ...Memory Map PXN20 Microcontroller Reference Manual Rev 1 A 118 Freescale Semiconductor...