SH7021 datasheet(105/509 Pages) RENESAS

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6.5

Notes

6.5.1

On-Chip Memory Instruction Fetch

Two instructions are 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.

6.5.2

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

Instruction fetch cycles: Conditional branch fetch

→ Next-instruction overrun fetch → Next-

instruction overrun fetch

→ Branch destination fetch

Instruction execution: Conditional branch instruction execution

→ Branch destination

instruction execution

2. TRAPA instruction, branch taken: TRAPA

Instruction fetch cycles: TRAPA instruction fetch

→ Next-instruction overrun fetch → Next-

instruction overrun fetch

→ Branch destination fetch

Instruction execution: TRAPA 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 does an overrun fetch.

When the next instruction or the one after that is set as a break condition, a branch will result in

the generation of a user break interrupt at the next instruction or the instruction after that, neither

of which instructions will be executed.

SH7021 Datasheet(PDF) 105 Page - Renesas Technology Corp