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B- 4 M68040 USER’S MANUAL MOTOROLA
MC68EC040
VCC
GND
BUS ARBITRATION
BG
BR
BB
BUS SNOOP CONTROL 
AND RESPONSE
M I
INTERRUPT 
CONTROL
IPL0
AVEC
IPEND
PROCESSOR 
CONTROL
CDIS
RSTI
RSTO
PCLK
BCLK
TEST
TRST
TMS
TCK
TDI
POWER SUPPLY
TDO
SC0
SC1
IPL1
IPL2
STATUS AND 
CLOCKS
PST0
PST1
PST2
DATA BUS D31–D0
TRANSFER
ATTRIBUTES
MASTER
TRANSFER
CONTROL
A31–A0
ADDRESS
BUS
TS
TIP
TCI
SLAVE
TRANSFER
CONTROL
TEA
TBI
R/W
LOCKE
CIOUT
TT0
TT1
TM0
TM1
TM2
TLN0
TLN1
UPA0
UPA1
SIZ0
SIZ1
LOCK
TA
PST3
JS0
JS1
Figure B-3. MC68EC040 Functional Signal Groups
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
implements as data transparent translation registers. The page size is fixed at
4 Kbytes.
PTEST and PFLUSH instructions cause an indeterminate result (i.e., an
undetermined number of bus cycles); the user should not execute them on the
MC68EC040.
The MC68EC040 does not contain an FPU, which causes unimplemented floating-
point exceptions to occur using a new stack frame format.
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