ADSP-2126x SHARC Processor Hardware Reference
3-21
Program Sequencer
Core Stalls
Like all previous SHARC processors, there are a number of conditions
that cause the core to temporarily stop fetching and executing further
instructions. This event, known as a
core stall
, occurs when an instruction
accesses a peripheral’s data-buffer. Specifically, the core stalls when it
reads an empty receive buffer or writes a full transmit buffer. Execution
resumes once the peripheral moves a valid word of data into the receive
buffer or when the peripheral sends one word out from the transmit
buffer.
In addition to standard core stall situations, there are four other condi-
tions that cause the ADSP-2126x core to stall. The following instructions
or sequences of instructions will cause the processor core to stall for one or
more cycles. These stalls were introduced to facilitate the doubling of the
core clock rate without modifying the 3-deep instruction-pipeline.
1. Reading or writing any memory mapped register in a conditional
instruction stalls the core for one cycle. This means that a total of
two cycles are needed for that instruction to complete.
2. Reading the System/Emulator memory-mapped registers shown in
stalls the processor for one cycle. Therefore, a total of
two cycles are needed for that instruction.
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 ...