MSC8144E Reference Manual, Rev. 3
14-20
Freescale
Semiconductor
Direct Memory Access (DMA) Controller
14.3.2 EDF Arbitration
EDF arbitration optimizes the DMA transactions in a time domain, simplifying application
development. The EDF algorithm assumes that the application needs certain data to be
transferred within a certain time. Every channel declares its deadline target, and the DMA
controller sorts all channels into four priority groups. The deadline is the time between the
current counter value (DMAEDFTDLx[CC]) to the threshold value (DMAEDFTDLx[TH]). See
page 14-30 for details. The features of EDF arbitration are as follows:
Round-robin arbitration with channels in the same group.
8-bit counter and base register for each channel
.
Counter is enabled/disabled when channel is activated/deactivated.
Two options for continued buffer:
— Continuous mode. Continues the deadline counter and channel with no action by the
EDF logic.
— Reset mode. Reloads the counter.
Maskable interrupt for threshold deadline crossing when an active counter crosses the
threshold.
Four optional clock sources for the counters and a DMA predivider.
Automatic channel priority group supporting DMA based on EDF algorithm.
The EDF sorts the channels into four priority groups according to their time to deadline value.
The arbitration between the groups is fixed-priority (lowest group number has the highest
priority). The arbitration among the channels in the same group is round-robin. Pairs of channels
with same priority in the same priority group are served according to their channel number, as
illustrated in Table 14-13 and Table 14-14.
Table 14-13. Channels Sorted Into Four Priority Groups
Time to Deadline
Priority Group
0–1
0
2–7
1
8–63
2
64–255
3
Table 14-14. Example of Channel Priority Sorting
Channel
Current
Count
Threshold
Time to
Deadline
Priority
Group
Priority (n)
Priority
(n+1)
Priority
(n+2)
Priority
(n+3)
0
100
0
100
3
1
0 (winner)
31
30
1
255
80
175
3
2
1
0 (winner)
31
2
255
80
175
3
2
1
0
0 (winner)
3
240
160
80
3
0 (winner)
31
30
29
Содержание MSC8144E
Страница 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Страница 40: ...MSC8144E Reference Manual Rev 3 xl Freescale Semiconductor Contents 26 5 12 8 RNG Output FIFO 26 186 ...
Страница 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Страница 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Страница 167: ...OCE Event and JTAG Test Access Port Signals MSC8144E Reference Manual Rev 3 Freescale Semiconductor 3 59 ...
Страница 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Страница 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Страница 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Страница 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Страница 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Страница 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Страница 884: ...MSC8144E Reference Manual Rev 3 17 44 Freescale Semiconductor RapidIO Interface Dedicated DMA Controller ...
Страница 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...