
Enhanced Direct Memory Access Controller (eDMA)
PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
24-23
A channel’s ability to preempt another channel can be disabled by setting EDMA_CPR[DPA]. When a
channel’s preempt ability is disabled, that channel cannot suspend a lower priority channel’s data transfer;
regardless of the lower priority channel’s ECP setting. This allows for a pool of low priority, large data
moving channels to be defined. These low priority channels can be configured to not preempt each other,
thus preventing a low priority channel from consuming the preempt slot normally available a true, high
priority channel.
24.3.2.17 Transfer Control Descriptor (TCD)
Each channel requires a 32-byte transfer control descriptor for defining the desired data movement
operation. The channel descriptors are stored in the local memory in sequential order: channel 0, channel
1,... channel 31. The definitions of the TCD are presented as eight 32-bit values.
of the basic TCD structure.
Offset:
EDM
n
Access: User read/write
0
1
2
3
4
5
6
7
R
ECP
DPA
GRPPRI
CHPRI
W
Reset
0
0
0
0
1
The reset value for the channel priority field, CHPRI[0–3], is equal to the corresponding channel number for each priority
register; that is, EDMA_CPRI0[CHPRI] = 0b0000 and EDMA_CPR15[CHPRI] = 0b1111.
Figure 24-17. eDMA Channel n Priority Register (EDMA_CPRn)
Table 24-18. EDMA_CPRn Field Descriptions
Field
Description
ECP
Enable Channel Preemption.
0 Channel n cannot be suspended by a higher priority channel’s service request.
1 Channel n can be temporarily suspended by the service request of a higher priority channel.
DPA
Disable preempt ability.
0 Channel n can suspend a lower priority channel.
1 Channel n cannot suspend any channel, regardless of channel priority.
GRPPRI[0:1]
Channel n current group priority. Group priority assigned to this channel group when fixed-priority arbitration
is enabled. These two bits are read-only; writes are ignored. The reset value for the group priority fields is equal
to the corresponding channel number for each priority register; that is, EDMA_CPR31[GRPPRI] = 0b01.
CHPRI[0:3]
Channel n Arbitration Priority. Channel priority when fixed-priority arbitration is enabled. The reset value for the
channel priority fields CHPRI[0–3], is equal to the corresponding channel number for each priority register; that
is, EDMA_CPR31[CHPRI] = 0b1111.
Table 24-19. TCDn 32-bit Memory Structure
eDMA Offset
TCDn Field
(32 x n)+0x0000
Source address (saddr)
(32 x n)+0x0004
Transfer attributes
Signed source address offset (soff)
(32 x n)+0x0008
Inner minor byte count (nbytes)
Содержание PXN2020
Страница 1: ...PXN20 Microcontroller Reference Manual Devices Supported PXN2020 PXN2120 PXN20RM Rev 1 06 2011...
Страница 42: ...PXN20 Microcontroller Reference Manual Rev 1 lxiv Freescale Semiconductor...
Страница 64: ...Introduction PXN20 Microcontroller Reference Manual Rev 1 1 22 Freescale Semiconductor...
Страница 112: ...Signal Description PXN20 Microcontroller Reference Manual Rev 1 3 44 Freescale Semiconductor...
Страница 118: ...Resets PXN20 Microcontroller Reference Manual Rev 1 4 6 Freescale Semiconductor...
Страница 162: ...Clocks Reset and Power CRP PXN20 Microcontroller Reference Manual Rev 1 6 30 Freescale Semiconductor...
Страница 182: ...Frequency Modulated Phase Locked Loop FMPLL PXN20 Microcontroller Reference Manual Rev 1 7 20 Freescale Semiconductor...
Страница 268: ...Boot Assist Module BAM PXN20 Microcontroller Reference Manual Rev 1 9 14 Freescale Semiconductor...
Страница 318: ...Interrupts and Interrupt Controller INTC PXN20 Microcontroller Reference Manual Rev 1 10 50 Freescale Semiconductor...
Страница 326: ...General Purpose Static RAM SRAM PXN20 Microcontroller Reference Manual Rev 1 11 8 Freescale Semiconductor...
Страница 372: ...e200z6 Core Z6 PXN20 Microcontroller Reference Manual Rev 1 13 8 Freescale Semiconductor...
Страница 412: ...e200z0 Core Z0 PXN20 Microcontroller Reference Manual Rev 1 14 14 Freescale Semiconductor...
Страница 460: ...Memory Protection Unit MPU PXN20 Microcontroller Reference Manual Rev 1 18 20 Freescale Semiconductor...
Страница 478: ...Error Correction Status Module ECSM PXN20 Microcontroller Reference Manual Rev 1 19 18 Freescale Semiconductor...
Страница 488: ...Software Watchdog Timer SWT PXN20 Microcontroller Reference Manual Rev 1 20 10 Freescale Semiconductor...
Страница 494: ...System Timer Module STM PXN20 Microcontroller Reference Manual Rev 1 21 6 Freescale Semiconductor...
Страница 821: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 27 49...
Страница 822: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 27 50 Freescale Semiconductor...
Страница 926: ...Controller Area Network FlexCAN PXN20 Microcontroller Reference Manual Rev 1 29 42 Freescale Semiconductor...
Страница 990: ...Deserial Serial Peripheral Interface DSPI PXN20 Microcontroller Reference Manual Rev 1 30 64 Freescale Semiconductor...
Страница 1044: ...Enhanced Serial Communication Interface eSCI PXN20 Microcontroller Reference Manual Rev 1 31 54 Freescale Semiconductor...
Страница 1080: ...Cross Triggering Unit CTU PXN20 Microcontroller Reference Manual Rev 1 33 12 Freescale Semiconductor...
Страница 1134: ...Analog to Digital Converter ADC PXN20 Microcontroller Reference Manual Rev 1 34 54 Freescale Semiconductor...
Страница 1150: ...IEEE 1149 1 Test Access Port Controller JTAGC PXN20 Microcontroller Reference Manual Rev 1 35 16 Freescale Semiconductor...
Страница 1257: ...Nexus Development Interface NDI PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 36 107...
Страница 1258: ...Nexus Development Interface NDI PXN20 Microcontroller Reference Manual Rev 1 36 108 Freescale Semiconductor...
Страница 1376: ...Memory Map PXN20 Microcontroller Reference Manual Rev 1 A 118 Freescale Semiconductor...