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
438
Section 15: JTAG and Debug
Document
1250_1125-UM100CB-R
A
DDRESS
R
EGISTER
The Address Register is 77 bits long and contains the address bits, byte enables, bus command and cache
attributes. To maintain coherency the cache attributes must be set correctly for the address so snoop
responses are correct (in some situations the debugger may want to use different attributes but it must do so
with care, for example a cacheable non-coherent read to a memory address can be used to force data to come
from the L2 cache or memory, never a processor L1 cache, and an uncacheable read from a memory address
will force the data to come from memory). The address is for a 32 byte cache block, the byte enables complete
selection within the block.
shows the Address Register, which is scanned starting with the LSB.
D
ATA
R
EGISTER
The Data Register contains 256 data bits, the status/error code, the ID of the agent that put the data on the
ZBbus, the modified flag, and (on reads) the response phase information for the transaction. The register is
shown in
, and is scanned from LSB to MSB. The mapping from the byte enables in the address
register to bits in this register is fixed; however, the byte address associated with each byte lane depends on
the system endian mode as shown in
Table 308: JTAG Address Register Scan Chain
Bits
ZBbus signal (see
)
Description
34:0
A_AD[39:5]
Address
66:35
A_BE[31:0]
Byte Enables. Indicate which byte lanes are valid in the Data Register, see
for the mapping from byte enable to byte address.
69:67
A_CMD[2:0]
Command. See
71:70
A_L1CA[1:0]
L1 Cacheability attribute. See
72
A_L2CA
L2 Cache Allocate request.
76:73
A_ID[9:6]
Requester agent ID (see
). These bits are only valid when the probe is
the slave, in master mode the SCD agent ID will be used for the transaction.
Table 309: Data Register Scan Chain
Bits
ZBbus signal (see
Description
255:0
D_DA[255:0]
Data. Only the byte lanes that had byte enables set contain valid data.
258:256
D_CODE[2:0]
Data status/error code (see
259
D_MOD
Set to indicate the data is modified (dirty).
263:260
D_RSP[3:0]
Id of Agent putting the data on the ZBbus. This is a read only field, bits scanned in will
be ignored.
264
R_L2HIT
Response indicating block is in the L2 cache (read only, only valid for probe master
reads).
270:265
R_EXC[5:0]
Response indicating block is exclusive in an agent (read only, only valid for probe master
reads).
276:271
R_SHD[5:0]
Response indicating block is shared by an agent (read only, only valid for probe master
reads).
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