9- 10
M68000 8-/16-/32-BIT MICROPROCESSORS USER'S MANUAL
MOTOROLA
Table 9-15. Conditional Instruction Execution Times
Instruction
Displacement
Branch Taken
Branch Not Taken
Bcc
Byte
10(2/0)
6(1/0)
Word
10(2/0)
BRA
Byte
10(2/0)
—
Word
10(2/0)
—
BSR
Byte
18(2/2)
—
Word
18(2/2)
—
DBcc
cc true
—
10(2/0)
cc false
10(2/0)
16(3/0)
9.9 JMP, JSR, LEA, PEA, AND MOVEM INSTRUCTION
EXECUTION TIMES
Table 9-16 lists the timing data for the jump (JMP), jump to subroutine (JSR), load
effective address (LEA), push effective address (PEA), and move multiple registers
(MOVEM) instructions. The total number of clock periods, the number of read cycles, and
the number of write cycles are shown in the previously described format.
Table 9-16. JMP, JSR, LEA, PEA, and MOVEM Instruction Execution Times
Instruction
Size
(An)
(An)+
–(An)
(d 16 ,An)
(d 8,An,Xn)+
(xxx) W
(xxx).L
(d 8 PC)
(d 16 , PC, Xn)*
JMP
—
8(2/0)
—
10 (2/0)
14 (3/0)
10 (2/0)
12 (3/0)
10 (2/0)
14 (3/0)
JSR
—
16 (2/2)
—
18 (2/2)
22 (2/2)
18 (2/2)
20 (3/2)
18 (2/2)
22 (2/2)
LEA
—
4(1/0)
—
8(2/0)
12 (2/0)
8(2/0)
12 (3/0)
8(2/0)
12 (2/0)
PEA
—
12 (1/2)
—
16 (2/2)
20 (2/2)
16 (2/2)
20 (3/2)
16 (2/2)
20 (2/2)
MOVEM
M
→ R
Word
12+4n
(3+n/0)
12+4n
(3+n/0)
—
16+4n
(4+n/0)
18+4n
(4+n/0)
16+4n
(4+n/0)
20+4n
(5+n/0)
16+4n
(4+n/0)
18+4n
(4+n/0)
Long
24+8n
(3+2n/0)
12+8n
(3+2n/0)
—
16+8n
(4+2n/0)
18+8n
(4+2n/0)
16+8n
(4+2n/0)
20+8n
(5+2n/0)
16+8n
(4+2n/0)
18+8n
(4+2n/0)
MOVEM
R
→ M
Word
8+4n
(2/n)
—
8+4n
(2/n)
12+4n
(3/n)
14+4n
(3/n)
12+4n
(3/n)
16+4n
(4/n)
—
Long
8+8n
(2/2n)
—
8+8n
(2/2n)
12+8n
(3/2n)
14+8n
(3/2n)
12+8n
(3/2n)
16+8n
(4/2n)
—
MOVES
M
→ R
Byte/
Word
18 (3/0)
20 (3/0)
20 (4/0)
24 (4/0)
20 (4/0)
24 (5/0)
Long
22 (4/0)
24 (4/0)
24 (5/0)
28 (5/0)
24 (5/0)
28 (6/0)
MOVES
R
→ M
Byte/
Word
18 (2/1)
20 (2/1)
20 (3/1)
24 (3/1)
20 (3/1)
24 (4/1)
Long
22 (2/2)
24 (2/2)
24 (3/2)
28 (3/2)
24 (3/2)
28 (4/2)
n is the number of registers to move.
*The size of the index register (Xn) does not affect the instruction's execution time.
9.10 MULTIPRECISION INSTRUCTION EXECUTION TIMES
Table 9-17 lists the timing data for multiprecision instructions. The numbers of clock
periods include the times to fetch both operands, perform the operations, store the results,
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