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ColdFire2/2M User’s Manual
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9-1
SECTION 9
INSTRUCTION EXECUTION TIMING
This section presents ColdFire2/2M instruction execution times in terms of clock cycles. The
number of operand references for each instruction is also included, enclosed in parentheses
following the number of clock cycles. Each timing entry is presented as
C
(r/w) where:
C
- The number of ColdFire2/2M clock cycles, including all applicable operand fetches
and writes, as well as all internal cycles required to complete the instruction execution.
r/w - The number of operand reads (r) and writes (w) required by the instruction. An
operation performing a read-modify-write function is denoted as (1/1).
This section includes assumptions concerning the timing values and the execution time
details and applies to both the ColdFire2 and ColdFire2M unless otherwise noted.
9.1 TIMING ASSUMPTIONS
The timing data presented in this section have the following assumptions:
1. The operand execution pipeline (OEP) is loaded with the opword and all required
extension words at the beginning of each instruction execution. This implies that the
OEP doesn’t wait for the instruction fetch pipeline (IFP) to supply opwords and/or
extension words.
2. The OEP does not experience any sequence-related pipeline stalls. For the ColdFire2/
2M, the most common example of this type of stall involves consecutive STORE
operations, excluding the MOVEM instruction. For all STORE operations (except
MOVEM), certain hardware resources within the ColdFire2/2M are marked as ‘busy’
for two clock cycles after the final DSOC cycle of the STORE instruction. If a
subsequent STORE instruction is encountered within this 2-cycle window, it will be
stalled until the resource again becomes available. Thus, the maximum pipeline stall
involving consecutive STORE operations is 2 cycles. The MOVEM instruction uses a
different set of resources and this stall does not apply.
3. The OEP completes all memory accesses without any stall conditions caused by the
memory itself. Thus, the timing details provided in this section assume an infinite zero-
wait state memory is attached to the ColdFire2/2M.
4. All operand data accesses are aligned on the same byte boundary as the operand
size: 16-bit operands aligned on 0-modulo-2 addresses, 32-bit operands aligned on 0-
modulo-4 addresses.
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