BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
82
Section 4: System Control and Debug Unit
Document
1250_1125-UM100CB-R
Table 52: Encoded Byte Enables for CPU Transactions
CPU Operation
DoubleWord
A_DW
Byte A_BYT
Comments
Cacheable fill or
evict or
Instruction Fetch
1111
11111111
Cacheable operations always move a full block, so the byte
enables can be ignored.
Uncacheable
Instruction Fetch
1100
0011
11111111
Uncacheable instruction fetches always fetch four
instructions (either the first or second half of a cache block).
Uncacheable lb/sb
One bit set
One bit set
The byte can be identified from the encoded enables.
Uncacheable lh/sh
One bit set
11000000
00110000
00001100
00000011
The half word can be identified from the encoded enables.
Uncacheable lw/sw
One bit set
11110000
00001111
The word can be identified from the encoded enables.
Uncacheable ld/sd
One bit set
11111111
The double word can be identified from the A_DW code.
Uncacheable
lwl/lwr/swl/swr
One bit set
1-4 bits set
The bytes can be identified from the encoded enables (but
some combinations will match word/halfword/byte
accesses).
Uncacheable
ldl/ldr/sdl/sdr
One bit set
1-8 bits set
The bytes can be identified from the encoded enables (but
some combinations will match double/word/halfword/byte
accesses).
Uncached
Accelerated Writes
1-4 bits set
1-8 bits set
If only doubleword stores are involved they can be
identified. If word stores are used then information may be
lost (reconstruction may be possible from the source code).