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ColdFire Core
Freescale Semiconductor
3-26
3.3.4.16
Precise Faults
To support a demand-paged virtual-memory environment, all memory references require precise,
recoverable faults. The ColdFire instruction restart mechanism ensures that a faulted instruction restarts
from the execution beginning. No internal state information is saved when an exception occurs nor is any
restored when the handler ends. Given the PC address defined in the exception stack frame, the processor
re-establishes program execution by transferring control to the given location as part of the RTE (return
from exception) instruction.
The instruction restart recovery model requires program-visible register changes made during execution
to be undone if that instruction subsequently faults.
The Version 4 (and later) ColdFire OEP structure naturally supports this concept for most instructions;
program-visible registers are updated only in the final OEP stage when fault collection is complete. If any
exception occurs, pending register updates are discarded.
For V4 ColdFire cores and later, most single-cycle instructions naturally support precise faults and
instruction restart, while complex instruction do not. Consider the following memory-to-memory move:
move.l
(Ay)+,(Ax)+
# copy 4 bytes from source to destination
This instruction takes one cycle to read the source operand (Ay) and one to write the data into Ax. Source
and destination address pointers are updated as part of execution.
lists the operations performed
in execute stage (EX).
7–3
SRAMSZ
SRAM bank size.
00000 No SRAM
00010 512 bytes
00100 1 KB
00110 2 KB
01000 4 KB
01010 8 KB
01100 16 KB
01111 24 KB
01110 32 KB (This is the value used for this device)
10000 64 KB
10010 128 KB
Else
Reserved for future use
2–0
Reserved.
Table 3-10. D1 Hardware Configuration Information Field Description (continued)
Field
Description
Summary of Contents for MCF54455
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Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
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