MIPS R10000 Microprocessor User's Manual - SGI TechPubs Library

System Interface Operations 95
6.13 System Interface Bus Encoding
SysCmd[11:0] Encoding
SysCmd[11] Encoding
This section presents the encoding of the following four System interface buses:
• SysCmd[11:0]
• SysAD[63:0]
• SysState[2:0]
• SysResp[4:0]
This section describes address and data cycle encodings for the system command
bus, SysCmd[11:0].
When SysVal* is asserted, SysCmd[11] indicates whether the SysAD[63:0] bus
represents an address or a data cycle, as shown in Table 6-2.
Table 6-2 Encoding of SysCmd[11]
SysCmd[10:0] Address Cycle Encoding
SysCmd[11] Data/Address Cycle Indication
0 SysAD[63:0] address cycle
1 SysAD[63:0] data cycle
During the address cycle of processor read and upgrade requests, SysCmd[10:8]
contain the request number, as shown in Table 6-3. The request number provides
a mechanism to associate an external response with the corresponding processor
request.
Table 6-3 Encoding of SysCmd[10:8] for Processor Read and Upgrade Requests
SysCmd[10:8] Request Number
MIPS R10000 Microprocessor User's Manual Version 2.0 of January 29, 1997