Error Logs 4-51
4.4.10
Command Codes
Table 4-9 shows the codes for transactions on the system bus and how they are
affected by the commander in charge of the bus during the transaction. The
command is a six-bit field in the command address (bits<5:0>). Bit-to-text
translations give six-bit data (although the top two bits may or may not be relevant).
Note that address bit<39> defines the command as being either a system space or an
I/O command.
Table 4-9 Decoding Commands
5 4
MC_C
MD
3 2 1 0
CMD
in
Hex
MC_
ADR
<39>
Description
No B-
Cache
CPU
B-
Cache
CPU
IOD
x x
0 0 0 0
X 0
1
Mem Idle
Y
Y
0 0
0 0 1 0
0 2
1
Write Pend Ack
Y
x x
0 0 1 1
X 3
1
Mem Refresh
x x
0 1 0 1
X 4
0
Set Dirty
Y
x 0
0 1 1 0
0/2 6
0
Write Thru - Mem
Y
Y
x 0
0 1 1 0
0/2 6
1
Write Thru - I/O
Y
Y
x 1
0 1 1 0
3/1 6
0
Write Back - Mem
Y
Y
x 1
0 1 1 0
3/1 6
1
Write Intr - I/O
Y
0 0
0 1 1 1
0 7
0
Write Full - Mem
Y
1 0
0 1 1 1
2 7
0
Write Part - Mem
(B-cache CPU
only)
Y
x 0
0 1 1 1
0/2 7
1
Write Mask - I/O
Y
x 0
0 1 1 1
0/2 7
0
Write Merge -
Mem
Y
x x
1 0 0 0
X 8
0
Read0 - Mem
Y
Y
Y
x x
1 0 0 0
X 8
1
Read0 - I/O
Y
Y
x x
1 0 0 1
X 9
0
Read1 - Mem
Y
Y
Y
x x
1 0 0 1
X 9
1
Read1 - I/O
Y
Y
x x
1 0 1 0
X A
0
Read Mod0 -
Mem
Y
Y
Y
