Operations With A Delay Slot - Fujitsu FR60 Hardware Manual

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CHAPTER 3 CPU AND CONTROL UNITS

Operations with a Delay Slot

This section describes operation when operations with a delay slot are specified for a

branch instruction.

■ Branch Instructions with Delay Slot

Instructions written as follows perform a branch operation with a delay slot:

■ Operation with Delay Slot

In an operation with a delay slot, the instruction immediately following the branch instruction (this is called

the delay slot) is executed, then the instruction at the branch destination is executed.

Since an instruction in the delay slot is executed before the branch operation, the apparent execution speed

is one cycle. However, a NOP instruction must be placed in the delay slot if there is no valid instruction put

If a conditional branch instruction is used, an instruction placed in the delay slot is executed whether or not

the condition for branching is met.

If a delay branch instruction is used, the order of execution for some instructions seems to be reversed.

However, this occurs only for updating the PC and the instructions are executed in the specified order for

other operations (register update and reference, etc.)

The following is a concrete example.

1) Ri referred by the JMP:D @Ri / CALL:D @Ri instruction is not affected even though Ri is updated by

the instruction in the delay slot.

List of instructions

Branch instruction

Delay slot ... Executed before branch

Branch destination

Mb91350a series