HD6417641 RENESAS [Renesas Technology Corp], HD6417641 Datasheet - Page 178

• Manufacturer Part Number: HD6417641
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 3 DSP Operation
Note 1: Actual Implementation
Repeat start and repeat end registers, RS and RE, specify the repeat start instruction and repeat end
instruction. The actual addresses that are kept in these registers depend on the number of
instructions in the repeat loop. The rule is as follows:
Repeat_Start:
Repeat_Start0:
Repeat_End3:
Table 3.17 RS and RE Setting Rule
Rev. 4.00 Sep. 14, 2005 Page 128 of 982
REJ09B0023-0400
RS
RE
RC > 1 :
1. 1 repeated step
4. 4 repeated steps
Start(End):
Start:
End:
RC = 0 :
Acceptable for any interrupts
A: Acceptable for any interrupts
B and C: Acceptable for some interrupts
1
Repeat_start0 + 8
Repeat_start0 + 4
_
Figure 3.18 Restriction of Interrupt Acceptance in Repeat Loop
instr – 1
instr0
instr1
instr2
instr – 1
instr0
instr1
instr2
instr3
instr4
instr4
An address of the instruction at the repeat top
An address of the instruction before one instruction at the repeat top
An address of the instruction before three instructions at the repeat bottom
; A
; B
; C
; A
; A
; A
; B
; C
; C
; C
; A
2
Repeat_start0 + 6
Repeat_start0 + 4
Number of Instructions in Repeat Loop
Start:
End:
2. 2 repeated steps
5. 5 or more repeated steps
Start:
End:
instr – 1
instr0
instr1
instr n – 3
instr n – 2
instr n – 1
instr n
instr n + 1
instr – 1
instr0
instr1
instr2
instr3
:
:
3
Repeat_start0 + 4
Repeat_start0 + 4
; A
; B
; C
; C
; A
; A
; A
; A
; B
; C
; C
; C
; A
Start:
End:
3. 3 repeated steps
≥4
Repeat_start
Repeat_End3 + 4
instr – 1
instr0
instr1
instr2
instr3
instr4
; A
; B
; C
; C
; C
; A