PXD20RM Datasheet, PDF (698/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

• This peripheral is programmed to be stopped in the required low power mode and active in RUN
Mode.
• AND this peripheral is active with a DMA transfer when software requests a transition to Low
Power mode.
To ensure correct operation, ensure that all the DMA enabled peripherals have completed their transfers
before requesting transition to low power mode.
17.5.3 Enabling and configuring sources
Enabling a source with periodic triggering
1. Determine with which DMA channel the source will be associated. Note that only the first 8 DMA
channels have periodic triggering capability.
2. Clear the ENBL and TRIG bits of the DMA channel
3. Ensure that the DMA channel is properly configured in the DMA. The DMA channel may be
enabled at this point
4. Configure the corresponding timer
5. Select the source to be routed to the DMA channel. Write to the corresponding CHCONFIG
register, ensuring that the ENBL and TRIG bits are set
Example 17-1. Configure source #5 Transmit for use with DMA Channel 2, with periodic triggering capability
1. Write 0x00 to CHCONFIG2 (Base Address + 0x02)
2. Configure Channel 2 in the DMA, including enabling the channel
3. Configure a timer for the desired trigger interval
4. Write 0xC5 to CHCONFIG2 (Base Address + 0x02)
The following code example illustrates steps #1 and #4 above:
In File registers.h:
#define DMAMUX_BASE_ADDR
0xFC084000/* Example only ! */
/* Following example assumes char is 8-bits */
volatile unsigned char *CHCONFIG0 = (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x0000);
volatile unsigned char *CHCONFIG1 = (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x0001);
volatile unsigned char *CHCONFIG2 = (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x0002);
volatile unsigned char *CHCONFIG3 = (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x0003);
volatile unsigned char *CHCONFIG4 = (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x0004);
volatile unsigned char *CHCONFIG5 = (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x0005);
volatile unsigned char *CHCONFIG6 = (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x0006);
volatile unsigned char *CHCONFIG7 = (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x0007);
volatile unsigned char *CHCONFIG8 = (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x0008);
volatile unsigned char *CHCONFIG9 = (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x0009);
volatile unsigned char *CHCONFIG10= (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x000A);
volatile unsigned char *CHCONFIG11= (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x000B);
volatile unsigned char *CHCONFIG12= (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x000C);
volatile unsigned char *CHCONFIG13= (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x000D);
volatile unsigned char *CHCONFIG14= (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x000E);
volatile unsigned char *CHCONFIG15= (volatile unsigned char *) (DMAMUX_BASE_ADDR+0x000F);
In File main.c:
#include "registers.h"
17-10
PXD20 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor