SH7052 datasheet(138/919 Pages) RENESAS

138 / 919 page

112

7.5

Usage Notes

7.5.1

Simultaneous Fetching of Two Instructions

Two instructions may be simultaneously fetched from on-chip memory. If a break condition is set

on the second of these two instructions but the contents of the UBC break condition registers are

changed so as to alter the break condition immediately after the first of the two instructions is

fetched, a user break interrupt will still occur when the second instruction is fetched.

7.5.2

Instruction Fetch at Branches

When a conditional branch instruction or TRAPA instruction causes a branch, instructions are

fetched and executed as follows:

1. Conditional branch instruction, branch taken: BT, BF

TRAPA instruction, branch taken: TRAPA

Instruction fetch order:

Branch instruction fetch

→ next instruction overrun fetch →

overrun fetch of instruction after next

→ branch destination

instruction fetch

Instruction execution order: Branch instruction execution

→ branch destination instruction

execution

2. When branching with a delayed conditional instruction: BT/S and BF/S instructions

Instruction fetch order:

Branch instruction fetch

→ next instruction fetch (delay slot) →

overrun fetch of instruction after next

→ branch destination

instruction fetch

Instruction execution order: Branch instruction execution

→ delay slot instruction execution

→ branch destination instruction execution

When a conditional branch instruction or TRAPA instruction causes a branch, the branch

destination will be fetched after the next instruction or the one after that performs an overrun

fetch. However, because the instruction that is the object of the break first breaks after a definite

instruction fetch and execution, the kind of overrun fetch instructions noted above do not become

objects of a break. If data access breaks are also included with instruction fetch breaks as break

conditions, a break occurs because the instruction overrun fetch is also regarded as becoming a

data break.

SH7052 Datasheet(PDF) 138 Page - Renesas Technology Corp