ADSP-BF50x Blackfin Processor Hardware Reference
7-63
Direct Memory Access
If all
DMACFG
fields in a descriptor chain have the
FLOW
and
NDSIZE
fields set
to zero, the individual DMA sequences do not start until triggered by soft-
ware. This is useful when the DMAs need to be synchronized with other
events in the system, and it is typically performed by interrupt service rou-
tines. A single MMR write is required to trigger the next DMA sequence.
Especially when applied to MDMA channels, such scenarios play an
important role. Usually, the timing of MDMAs cannot be controlled (see
“Handshaked Memory DMA Operation” on page 7-37
). By halting
descriptor chains or rings this way, the whole DMA transaction can be
broken into pieces that are individually triggered by software.
Source and destination channels of a MDMA may differ in descrip-
tor structure. However, the total work count must match when the
DMA stops. Whenever a MDMA is stopped, destination and
source channels should both provide the same
FLOW
= 0 mode after
exactly the same number of words. Accordingly, both channels
need to be started afterward.
Software-triggered descriptor fetches are illustrated in
Listing 7-7 on
page 7-98
. MDMA channels can be paused by software at any time by
writing a 0 to the
DRQ
bit field in the
HMDMAx_CONTROL
register. This simply
disables the self-generated DMA requests, whether or not the HMDMA is
enabled.
DMA Registers
DMA registers fall into three categories:
• DMA channel registers
• Handshaked MDMA registers
• Global DMA traffic control registers
Содержание EZ-KIT Lite ADSP-BF506F
Страница 50: ...Contents l ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 92: ...Development Tools 1 30 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 110: ...Interface Overview 3 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 132: ...Unique Information for the ADSP BF50x Processor 4 22 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 236: ...Internal Flash Memory Control Registers 6 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 342: ...Unique Information for the ADSP BF50x Processor 7 106 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 484: ...Unique Information for the ADSP BF50x Processor 10 60 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 493: ...ADSP BF50x Blackfin Processor Hardware Reference 11 9 Core Timer Unique Information for the ADSP BF50x Processor None ...
Страница 494: ...Unique Information for the ADSP BF50x Processor 11 10 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 506: ...Unique Information for the ADSP BF50x Processor 12 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 544: ...Unique Information for the ADSP BF50x Processor 13 38 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 650: ...Programming Examples 15 56 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 712: ...Unique Information for the ADSP BF50x Processor 16 62 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 804: ...Programming Examples 17 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 972: ...Unique Information for the ADSP BF50x Processor 20 38 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1194: ...Programming Examples 24 90 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1256: ...ACM Registers A 50 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1264: ...Boundary Scan Architecture B 8 ADSP BF50x Blackfin Processor Hardware Reference ...