Instruction Execution Timing
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
9-7
9.2.1
Load/Store Instruction Timing
Table 9-2. summarizes load/store instruction timings. This table assumes zero wait-state memory
references on a parked bus and pipelined external memory accesses.
Order memory access:
eieio
1
LSU
Next load/store
is synchronized
with ones before
Cache control:
icbi
1
LSU,
I-cache
No
1
Although a store (as well as
mtspr
for SPRs external to the core) issued to the LSU buffer frees the core pipeline, the
next load or store is not performed on the bus until it is free.
2
See
Table 4-5
.
3
Refer to
Chapter 4, “MPC8xx Core Register Set.”
4
See
Section 4.1.1.1.1, “Condition Register (CR),”
and
Section 4.1.2.3.1, “Machine State Register (MSR).”
5
6
Division blockage = division latency.
7
Blockage of the multiply instruction is dependent on the next instruction.If the next instruction is a divide, the blockage
is 2 clocks; otherwise, the blockage is 1 clock.
8
Assumes nonspeculative aligned access, on-chip memory, and available bus. See
Section 3.6.3.4, “Nonspeculative
Load Instructions,”
Section 3.6.3.5, “Unaligned Accesses,”
and
Section 9.2.1, “Load/Store Instruction Timing.”
Table 9-2. Load/Store Instruction Timing
Instruction Type
Latency Cleared
from
LSU
Data Cache External Memory Data Cache External Memory
Integer single target register load (aligned)
2 cycles
5 cycles
2 cycles
5 cycles
Integer single target register store (aligned)
1 cycle
1 cycle
2 cycles
5 cycles
Load/store multiple
1 + N
1
1
N denotes the number of registers transferred.
1 + N
Table 9-1. Instruction Execution Timing (continued)
Instructions
Latency
Blockage
Unit
Serializing
DivisionLatency
NoO verflow
3
⇒
34 divisorLength
–
4
------------------------------------------------------
⎝
⎠
⎛
⎞
+
Overflow
2
⇒
------------------------------------------------------------------------------------------------------------------------
=
Where
Overflow
x
0
---
⎝ ⎠
⎛ ⎞
or
MaxNegativeNumber
1
–
--------------------------------------------------
⎝
⎠
⎛
⎞
=
3 N
N 1
+
3
--------------
⎝
⎠
⎛
⎞
+ +
3 N
N 1
+
3
--------------
⎝
⎠
⎛
⎞
+ +
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