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Individual Instruction Descriptions
4-84
4.14.7 BEGLOOP Begin Loop
Syntax
[label] name
Clock,
clk
Word,
w
With RPT,
clk
Class
BEGLOOP
†
1 1 N/R 9d
†
Loop must end with ENDLOOP.
Execution Save next instruction address (PC + 1)
(
mask interrupts
)
PC ⇐ PC + 1
Flags Affected none
Opcode
Instructions 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
BEGLOOP 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0
Description This instruction saves the next sequential address in a shadow register and
masks interrupts. Interrupts occurring during execution of this and following
instructions are actually queued until the loop is complete (see ENDLOOP).
The loop executes N number of times. Thus, N – 2, should be loaded in R4
in order to loop N times.
BEGLOOP and ENDLOOP block has following restrictions:
No CALL instructions can be used.
All maskable interrupts are queued.
BEGLOOP/ENDLOOP block cannot be nested.
See Also ENDLOOP
Example 4.14.7.1 MOV R4, count – 2 ;init R4 with loop count
BEGLOOP
ADD A0, A0~, A0 ;add A0~ to A0 (count) times
ENDLOOP
Initialize R4 with the loop count value minus 2 to repeat the loop for count times. Execute the ADD A0,
A0~, A0 instruction until R4 is negative. R4 is decremented each time ENDLOOP is encountered. When
R4 is negative, ENDLOOP becomes a NOP and execution continues with the next instruction after
ENDLOOP.