DEC AlphaServer 8200 Technical Manual page 59

Table 2-9 describes the mailbox data structure.
Table 2-9 Mailbox Data Structure
QW Bit(s) Name
<29:0> CMD
0
<30> B
<31> W
<39:32> MASK
<47:40> MBZ
<55:48> HOSE
<63:56> MBZ
<63:0> RBADR
1
<63:0> WDATA
2
<63:0>
3
<63:0> RDATA
4
5 <0> DON
<1> ERR
<63:2> STATUS
<63:0>
6
<63:0>
7
The mailbox address is a 64-byte aligned memory location. The I/O mod-
ule is required to update only the RDATA and STATUS fields in this
Description
Remote Bus Command. Controls the remote bus opera-
tion and can include fields such as address only, address
width, and data width. See Alpha SRM.
Remote Bridge Access. If set, the command is a special
or diagnostic command directed to the remote side. See Al-
pha SRM.
Write Access. If set, the remote bus operation is a write.
Disable Byte Mask. Disables bytes within the remote bus
address. Mask bit <i> set causes the byte to be disabled;
for example, data byte <i> will NOT be written to the re-
mote address. See Alpha SRM.
Must be zero.
Hose. Specifies the remote bus to be accessed. Bridges can
connect to a maximum of 256 remote buses.
Must be zero.
Remote Bus Address. Contains the target address of the
device on the remote bus. See Alpha SRM.
Write Data. For write commands, contains the data to be
written. For read commands, the field is not used by the
bridge.
Unpredictable.
Read Data. For read commands, contains the data re-
turned. Unpredictable for write data commands.
Done. For read commands, indicates that the <ERR>,
<STATUS>, and <RDATA> fields are valid. For all com-
mands, indicates that the mailbox structure may be safely
modified by host software.
Error. If set on a read command, indicates that an error
was encountered. Valid only on read commands and when
<DON> is set. This field is Unpredictable on write com-
mands. See Alpha SRM.
Operation Completion Status. Contains information
specific to the bridge implementation. Valid only on read
commands and when <DON> is set. This field is Unpredict-
able on write commands.
Unpredictable.
Unpredictable.
TLSB Bus 2-31