SH7721 datasheet(301/1524 Pages) RENESAS

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Section 7 Exception Handling

Rev. 3.00 Jan. 18, 2008 Page 239 of 1458

REJ09B0033-0300

• User break before instruction execution

A user break before instruction execution is accepted at instruction [B], and an address of

instruction [B] is saved in the SPC. This exception cannot be accepted at instruction [C] but

the exception request is retained until an instruction [A] or [B] is executed at the next time.

Then, the exception request is accepted before an instruction [A] or [B] is executed. In this

case, an address of instruction [A] or [B] is saved in the SPC.

• User break after instruction execution

A user break after instruction execution cannot be accepted at instructions [B] and [C] but the

exception request is retained until an instruction [A] or [B] is executed at the next time. Then,

the exception request is accepted before an instruction [A] or [B] is executed. In this case, an

address of instruction [A] or [B] is saved in the SPC.

Table 7.4

Exception Acceptance in the Repeat Loop

Exception Type

Instruction [B]

Instruction [C]

Interrupt

Not accepted

DMA address error

Not accepted

User break before instruction execution

Accepted

Not accepted

User break after instruction execution

Not accepted

(4)

CPU Address Error in Repeat Control Period

If a CPU address error occurs in the repeat control period, the exception is accepted but an

exception code (H'070) indicating the repeat loop period is specified in the EXPEVT. If a CPU

address error occurs in instructions following a repeat detection instruction to repeat end

instruction, an exception code for instruction access or data access is specified in the EXPEVT.

The SPC is saved according to the description, SPC Saved by an Exception in Repeat Control

Period in section 7.4.3, Exception in Repeat Control Period.

After the CPU address error exception processing, the repeat control cannot be returned correctly.

To execute a repeat loop correctly, care must be taken not to generate a CPU address error in the

repeat control period.

Note:

In a repeat loop consisting of one to three instructions, some restrictions apply to repeat

detection instructions and all the remaining instructions. In a repeat loop consisting of four

or more instructions, restrictions apply to only the three instructions that include a repeat

end instruction. The restriction occurs when SR.RC[11:0]

≥ 1.

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