Excalibur electronic A-MNL-NIOSPROG-01.1 manual Direct CWP Manipulation

Overview

After branch instruction (b) is taken, instruction (c) is executed before control is transferred to the branch target (e). The execution sequence of the above code fragment would be (a), (b), (c), and (e). Instruction (c) is instruction (b)’s branch delay slot. Instruction (d) is not executed. Most instructions can be used as a branch delay slot except for those listed below:

■BR

■BSR

■CALL

■IF1

■IF0

■IFRnz

■IFRz

■IFS

■JMP

■LRET

■PFX

■RET

■SKP1

■SKP0

■SKPRnz

■SKPRz

■SKPS

■TRET

■TRAP

Direct CWP Manipulation

Every WRCTL instruction that modifies the STATUS register (%ctl0) must be followed by a NOP instruction.

24 Altera Corporation