B-2
M68040 USER鈥橲 MANUAL
MOTOROLA
MC68EC040 REV2.3 (01/31/2000)
With the exception of the memory management unit (MMU), the oating-point unit (FPU),
and their respective registers, the MC68EC040 programming model, data formats and
types, instruction set (except all instructions beginning with an 鈥淔鈥�, PTEST, and PFLUSH),
and caches are the same as described in Section 1 Introduction for the MC68040. Figures
B-2 and B-3 illustrate the programming model and functional signal groups for the
MC68EC040.
B.1 MC68EC040 DIFFERENCES
The following differences exist between the MC68EC040 and MC68040:
Two independent access control units (ACUs) replace the MC68040 MMUs. The ACU
has four corresponding registers (access control registers) that the MC68040 imple-
ments as data transparent translation registers. The page size is fixed at 4 Kbytes.
Figure B-1. MC68EC040 Block Diagram
INSTRUCTION MEMORY MANAGEMENT UNIT
DATA MEMORY MANAGEMENT UNIT
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INSTRUCTION
CACHE/ACCESS/SNOOP
CONTROLLER
INSTRUCTION
ATC
INSTRUCTION
CACHE
INSTRUCTION DATA BUS
OPERAND DATA BUS
DATA
CACHE/ACCESS/SNOOP
CONTROLLER
DATA
ATC
DATA
CACHE
INTEGER UNIT
INSTRUCTION
FETCH
DECODE
EFFECTIVE
ADDRESS
CALCULATE
EFFECTIVE
ADDRESS
FETCH
EXECUTE
WRITE-BACK
ADDRESS
BUS
DATA
BUS
CONTROL
SIGNALS
DATA
ADDRESS
INSTRUCTION
ADDRESS
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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