MC68EC040RC25 Freescale Semiconductor, MC68EC040RC25 Datasheet - Page 146

• Manufacturer Part Number: MC68EC040RC25
• Manufacturer: Freescale Semiconductor

Specifications of MC68EC040RC25

• Family Name: M68000
• Device Core: ColdFire
• Device Core Size: 32b
• Frequency (max): 25MHz
• Instruction Set Architecture: RISC
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Through Hole
• Pin Count: 179
• Package Type: PGA
• Lead Free Status / Rohs Status: Supplier Unconfirmed

Table 7-1 lists the combinations of the SIZx, A1, and A0 signals, collectively called byte
enable signals, that are used for each of the four sections of the data bus. In the table,
BYTEn indicates the data bus section that is active, the portion of the requested operand
that is read or written during that bus transfer. For line transfers, all bytes are valid as
listed and can correspond to portions of the requested operand or to data required to fill
the remainder of the cache line. The bytes labeled with a dash are not required; they are
ignored on read transfers and driven with undefined data on write transfers. Not selecting
these bytes prevents incorrect accesses in sensitive areas such as I/O devices. Figure 7-4
illustrates a logic diagram for one method for generating byte enable signals from the
SIZx, A1, and A0 and the associated PAL equation. These byte enable signals can be
combined with the address decode logic.
7-4
MULTIPLEXER
REGISTER
EXTERNAL
DATA BUS
ADDRESS
$xxxxxxx0
Long Word
Transfer
Word
Size
Byte
Line
Table 7-1. Data Bus Requirements for Read and Write Cycles
31
31
SIZ1
D31–D24
0
0
0
0
1
1
0
1
BYTE 3
BYTE 3
Signal Encodings
Freescale Semiconductor, Inc.
SIZ0
1
1
1
1
0
0
0
1
For More Information On This Product,
24 23
24 23
Figure 7-3. Data Multiplexing
A1
0
0
1
1
0
1
X
X
M68040 USER’S MANUAL
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A0
D23–D16
BYTE 2
0
1
0
1
0
0
X
X
BYTE 2
D31–D24
BYTEn
BYTEn
BYTEn
BYTEn
—
—
—
—
ROUTING
16 15
16 15
Active Data Bus Sections
D23–D16
BYTE n
BYTEn
BYTEn
BYTEn
D15–D8
BYTE 1
BYTE 1
—
—
—
—
8 7
8 7
D15–D8
BYTEn
BYTEn
BYTEn
BYTEn
—
—
—
—
BYTE 0
BYTE 0
D7–D0
BYTEn
BYTEn
BYTEn
BYTEn
D7–D0
—
—
—
—
MOTOROLA
0
0
EXTERNAL BUS
INTERNAL TO
THE MC68040