MC68EC040RC25 Freescale Semiconductor, MC68EC040RC25 Datasheet - Page 68

• 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

3.2.4.3 TABLE PAGING. The entire translation table for an active task need not be
resident in main memory. In the same way that only the working set of pages must be
allocated in main memory, only the tables that describe the resident set of pages need be
available. Placing the invalid code ($0 or $1) in the UDT field of the table descriptor that
points to the absent table(s) implements this paging of tables. When a task attempts to
use an address that an absent table would translate, the M68040 is unable to locate a
translation and takes access error exception when the execution unit retries the bus
access that caused the table search to be initiated.
The operating system determines that the invalid code in the descriptor corresponds to
nonresident tables. This determination can be facilitated by using he unused bits in the
descriptor to store status information concerning the invalid encoding. The M68040 does
not interpret or modify an invalid descriptor’s fields except for the UDT field. This
MOTOROLA
TASK A
TASK B
ADDRESS OFFSET =
* Page frame address shared by task A and B; write protected from task A.
TABLE ENTRY # =
$76543210 =
ROOT POINTER
ROOT POINTER
Figure 3-15. Translation Table Using Shared Tables
0 1 1 1 0 1 1 0 0 1 0 1 0 1 0 0 0 0 1 X X X X X X X X X X X X X
ROOT INDEX
Freescale Semiconductor, Inc.
$EC
$3B
For More Information On This Product,
$3B
Go to: www.freescale.com
M68040 USER'S MANUAL
W-BIT CLEAR
ROOT-LEVEL
POINTER INDEX
TABLE $00
W-BIT SET
TABLES
$15
$54
LOGICAL ADDRESS
PAGE INDEX
$15
$01
$04
POINTER-LEVEL
TABLE $3B
TABLE $00
$00003000
TABLES
PAGE OFFSET
$01
FRAME ADDRESS*
PAGE-LEVEL
TABLE $15
TABLE $00
TABLES
3- 19