
8-12
ColdFire CF4e Core User’s Manual
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Local Memory Connection Specification
The krom0csb and krom1csb signals are chip-selects for the KROMs. When a signal is
inactive, all other corresponding KROM signals are don’t cares. If multiple array instances
are used to implement the KROM array configuration, the signal must be used as the chip
enable for all instances.
8.4.1.3
Instruction Cache Information
The instruction cache controller uses synchronous SRAM memory arrays external to the
core for its memory array needs. These arrays must use the same clock as the core.
The instruction cache design contains a non-blocking, 4-way set-associative instruction
cache with a 16-byte line. Cache size is configurable with 2, 4, 8, 16, or 32 Kbyte capacities
available. The cache improves system performance by providing low-latency data to the
core instruction fetch pipeline, decoupling processor performance from system memory
response speeds and providing increased bus availability for alternate bus masters.
The non-blocking cache services read hits from the processor while a fill (caused by a cache
allocation) is in progress.
The instruction cache is virtual address indexed and physical address tagged (see
Chapter 10, “Memory Management Unit (MMU),” for detailed information). If the address
matches one of the cache entries, the access hits in the cache. For a read operation, the cache
supplies the data to the processor. If the access does not match one of the cache entries
Table 8-8. KROM Array Address Connection
krom{0,1}size[3:0]
Total Size
Configuration
Array Address
Unused Address
0000
0 bytes
KROM0 disabled
KROM1 disabled
—
krom0addr[15:2]
krom1addr[15:2]
0001
512 bytes
128 X 4 bytes
128 X 4 bytes
krom0addr[8:2]
krom1addr[8:2]
krom0addr[15:9]
krom1addr[15:9]
0010
1 Kbytes
256 X 4 bytes
256 X 4 bytes
krom0addr[9:2]
krom1addr[9:2]
krom0addr[15:10]
krom1addr[15:10]
0011
2 Kbytes
512 X 4 bytes
512 X 4 bytes
krom0addr[10:2]
krom1addr[10:2]
krom0addr[15:11]
krom1addr[15:11]
0100
4 Kbytes
1024 X 4 bytes
1024 X 4 bytes
krom0addr[11:2]
krom1addr[11:2]
krom0addr[15:12]
krom1addr[15:12]
0101
8 Kbytes
2048 X 4 bytes
2048 X 4 bytes
krom0addr[12:2]
krom1addr[12:2]
krom0addr[15:13]
krom1addr[15:13]
0110
16 Kbytes
4096 X 4 bytes
4096 X 4 bytes
krom0addr[13:2]
krom1addr[13:2]
krom0addr[15:14]
krom1addr[15:14]
0111
32 Kbytes
8192 X 4 bytes
8192 X 4 bytes
krom0addr[14:2]
krom1addr[14:2]
krom0addr[15]
krom1addr[15]
1000
64 Kbytes
16384 X 4 bytes
16384 X 4 bytes
krom0addr[15:2]
krom1addr[15:2]
—
—
1001–1111
RFU
RFU
RFU
RFU
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