SH7713 datasheet(130/904 Pages) RENESAS

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Section 3 DSP Operating Unit

Rev.1.50 Aug. 30, 2006 Page 90 of 860

REJ09B0288-0150

• Example 3: Repeat loop consisting of two instructions

LDRS RptStart

; Sets repeat start instruction address

to the RS register

LDRE RptEnd

; Sets repeat end instruction address

to the RE register

LDRC #4

; Sets the number of repetitions (4) to

the RC[11:0] bits of the SR register

instr0

; At least one instruction is required

from LDRC instruction to [Repeat start

instruction]

RptStart: instr1

; [Repeat start instruction]

RptEnd:

instr2

; [Repeat end instruction]

• Example 4: Repeat loop consisting of one instructions

LDRS RptStart

; Sets repeat start instruction address

to the RS register

LDRE RptEnd

; Sets repeat end instruction address

to the RE register

LDRC #4

; Sets the number of repetitions (4) to

the RC[11:0] bits of the SR register

instr0

; At least one instruction is required

from LDRC instruction to [Repeat start

Rptstart:

instruction] RptStart:

RptEnd:

instr1

; [Repeat start instruction]=

[Repeat end instruction]

In extended repeat control instructions, a repeat start instruction address and a repeat end

instruction address are stored in the RS register and RE register, respectively, regardless of the

number of repeat instructions. In addition, the extended repeat control can be performed by using

the LDRC instruction instead of the SETRC instruction. During the extended repeat control, a

repeat loop can be recognized by executing a repeat end instruction. Therefore, there is no

restriction on branches or exceptions.

Extended Repeat Control Instructions: To describe the extended repeat loop, the repeat start

and end addresses must be specified to the RS and RE registers by the LDRS and LDRE

instructions, respectively. For the LDRS and LDRE instructions of the extended repeat control

instructions, the LDRS and LDRE instructions of the compatible repeat control instructions are

used. The number of repetitions are specified by the LDRC instruction. An 8-bit immediate data or

the general register values can be used as an operand of the LDRC instruction. If 256 or greater

value is specified to the RC, use the LDRC Rm type instructions.

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