ADSP-2126x SHARC Processor Hardware Reference
7-19
I/O Processor
The I/O processor determines which DMA channel has the highest prior-
ity internal DMA request during every cycle between each data transfer.
Processor core accesses of I/O processor registers and TCB chain loading
(both of which occur after the IOD transfer) are subject to the same prior-
itization scheme as the DMA channels. Applying this scheme uniformly
prevents I/O bus contention, because these accesses are also performed
over the internal I/O bus. For more information, see
DMA Bus Arbitration
DMA channel arbitration is the method that the IOP uses to determine
how groups rotate priority with other channels. This feature is enabled by
setting the
DCPR
bit in the IOP’s
SYSCTL
register.
DMA-capable peripherals execute DMA data transfers to and from inter-
nal memory over the IOD bus. When more than one of these peripherals
requests access to the IOD bus in a clock cycle, the bus arbiter, which is
attached to the IOD bus, determines which master should have access to
the bus and grants the bus to that master.
IOP channel arbitration can be set to use either a
fixed
(
SYSCTL[7]
= 0) or
rotating
(
SYSCTL[7]
= 1) algorithm.
In the fixed priority scheme, the lower indexed peripheral has the highest
priority.
In the rotating priority scheme, the default priorities at reset are the same
as that of the fixed priority. However, the peripheral priority is deter-
mined by group, not individually. Peripheral groups are shown in
.
Initially, Group A has the highest priority and Group F the lowest. As one
group completes its DMA operation, it is assigned the lowest priority
(moves to the back of the line) and the next group is given the highest
priority.
Summary of Contents for ADSP-21261 SHARC
Page 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Page 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Page 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Page 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Page 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Page 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Page 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Page 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Page 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Page 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Page 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Page 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...