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ColdFire CF4e Core User’s Manual
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Cache Overview
Table 8-33 shows transitions when the previous state is valid.
Table 8-34 shows transitions when the previous state is modified.
Table 8-32. Data Cache Line State Transitions (Previous State Invalid)
Access
Response
Read miss
CI1,
WI1
Read line from memory and update cache;
supply data to processor;
go to valid state.
Read hit
CI2,
WI2
Not possible
Write miss (copyback)
CI3
Read line from memory and update cache;
write data to cache;
go to modified state.
Write miss (write-through)
WI3
Write data to memory;
stay in invalid state.
Write hit (copyback)
CI4
Not possible
Write hit (write-through)
WI4
Not possible
Cache invalidate
CI5,
WI5
No action;
stay in invalid state.
Cache push
CI6,
WI6
No action;
stay in invalid state.
Cache push
CI7,
WI7
No action;
stay in invalid state.
Table 8-33. Data Cache Line State Transitions (Previous State Valid)
Access
Response
Read miss
CV1,
WV1
Read new line from memory and update cache;
supply data to processor; stay in valid state.
Read hit
CV2,
WV2
Supply data to processor;
stay in valid state.
Write miss (copyback)
CV3
Read new line from memory and update cache;
write data to cache;
go to modified state.
Write miss (write-through)
WV3
Write data to memory;
stay in valid state.
Write hit (copyback)
CV4
Write data to cache;
go to modified state.
Write hit (write-through)
WV4
Write data to memory and to cache;
stay in valid state.
Cache invalidate
CV5,
WV5
No action;
go to invalid state.
Cache push
CV6,
WV6
No action;
go to invalid state.
Cache push
CV7,
WV7
No action;
stay in valid state.
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