Program Sequencer - Analog Devices ADSP-21261 SHARC Hardware Reference Manual

3 PROGRAM SEQUENCER

The DSP's program sequencer controls program flow by constantly pro-
viding the address of the next instruction to be fetched for execution.
Program flow in the DSP is mostly linear, with the processor executing
instructions sequentially. This linear flow varies occasionally when the
program branches due to nonsequential program structures, such as those
shown below. Nonsequential structures direct the DSP to execute an
instruction that is not at the next sequential address following the current
instruction. These structures include:
• Loops. One sequence of instructions executes multiple times with
zero overhead.
• Subroutines. The traditional
cessor temporarily breaks sequential flow to execute instructions
from another part of program memory.
• Jumps. Program flow is permanently transferred to another part of
program memory.
• Interrupts. A runtime event (generally not an instruction) triggers
the program sequencer to branch to interrupt-handling
subroutines.
• Idle. An instruction that causes the core to stop executing further
instructions and hold its current state until an interrupt occurs.
Then, after the processor services the interrupt, the sequencer
resumes normal program execution.
ADSP-2126x SHARC Processor Hardware Reference
/ structure where the pro-
CALL RETURN
3-1