Motorola M68000 - Bit Manipulation Instruction Execution Times; Conditional Instruction Execution Times

MOTOROLA MC68000 8-/16-/32-MICROPROCESSORS USER’S MANUAL 8- 7
8.7 BIT MANIPULATION INSTRUCTION EXECUTION TIMES
Table 8-8 lists the timing data for the bit manipulation 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. The number of clock periods, the number of read cycles, and
the number of write cycles, respectively, must be added to those of the effective address
calculation where indicated by a plus sign (+).
Table 8-8. Bit Manipulation Instruction Execution Times
Dynamic Static
Instruction Size Register Memory Register Memory
BCHG Byte — 8(1/1)+ — 12(2/1)+
Long 8(1/0)* — 12(2/0)* —
BCLR Byte — 8(1/1)+ — 12(2/1)+
Long 10(1/0)* — 14(2/0)* —
BSET Byte — 8(1/1)+ — 12(2/1)+
Long 8(1/0)* — 12(2/0)* —
BTST Byte — 4(1/0)+ — 8(2/0)+
Long 6(1/0) — 10(2/0) —
+Add effective address calculation time.
* Indicates maximum value; data addressing mode only.
8.8 CONDITIONAL INSTRUCTION EXECUTION TIMES
Table 8-9 lists the timing data for the conditional 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 8-9. Conditional Instruction Execution Times
Instruction Displacement
Branch
Taken
Branch Not
Taken
Bcc Byte 10(2/0) 8(1/0)
Word 10(2/0) 12(2/0)
BRA Byte 10(2/0) —
Word 10(2/0) —
BSR Byte 18(2/2) —
Word 18(2/2) —
DBcc cc true — 12(2/0)
cc false, Count Not Expired 10(2/0) —
cc false, Counter Expired — 14(3/0)
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