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Cache
Freescale Semiconductor
6-23
Table 6-6. Data Cache Line State Transitions
Access
Current State
Invalid (V = 0)
Valid (V = 1, M = 0)
Modified (V = 1, M = 1)
Read
miss
(C,W)I1 Read line from memory and
update cache;
supply data to processor;
go to valid state.
(C,W)V1 Read new line from memory
and update cache;
supply data to processor;
stay in valid state.
CD1
Push modified line to buffer;
read new line from memory
and update cache;
supply data to processor;
write push buffer contents to
memory;
go to valid state.
Read hit
(C,W)I2 Not possible.
(C,W)V2 Supply data to processor;
stay in valid state.
CD2
Supply data to processor;
stay in modified state.
Write
miss
(copy-
back)
CI3
Read line from memory and
update cache;
write data to cache;
go to modified state.
CV3
Read new line from memory
and update cache;
write data to cache;
go to modified state.
CD3
Push modified line to buffer;
read new line from memory
and update cache;
write push buffer contents to
memory;
stay in modified state.
Write
miss
(write-
through)
WI3
Write data to memory;
stay in invalid state.
WV3
Write data to memory;
stay in valid state.
WD3
Write data to memory;
stay in modified state.
Cache mode changed for
the region corresponding to
this line. To avoid this state,
execute a CPUSHL
instruction or set
CACR[DCINVA,ICINVA]
before switching modes.
Write hit
(copy-
back)
CI4
Not possible.
CV4
Write data to cache;
go to modified state.
CD4
Write data to cache;
stay in modified state.
Write hit
(write-
through)
WI4
Not possible.
WV4
Write data to memory and to
cache;
stay in valid state.
WD4
Write data to memory and to
cache;
go to valid state.
Cache mode changed for
the region corresponding to
this line. To avoid this state,
execute a CPUSHL
instruction or set
CACR[DCINVA,ICINVA]
before switching modes.
Cache
invalidate
(C,W)I5 No action;
stay in invalid state.
(C,W)V5 No action;
go to invalid state.
CD5
No action (modified data
lost);
go to invalid state.
Cache
push
(C,W)I6(
C,W)I7
No action;
stay in invalid state.
(C,W)V6 No action;
go to invalid state.
CD6
Push modified line to
memory;
go to invalid state.
(C,W)V7 No action;
stay in valid state.
CD7
Push modified line to
memory;
go to valid state.
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
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 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...