Mips Technologies R4000 - System Interface Command Syntax

MIPS R4000 Microprocessor User's Manual 365
System Interface
System Interface Command Syntax
This section describes the SysCmd bus encoding for System interface
commands. Figure 12-42 shows a common encoding used for all System
interface commands.
Figure 12-42 System Interface Command Syntax Bit Definition
SysCmd(8) must be set to 0 for all System interface commands.
SysCmd(7:5)specify the System interface request type which may be read,
write, null, invalidate, update, intervention, or snoop; Table 12-11 lists the
encoding of SysCmd(7:5).
Table 12-11 shows the types of requests encoded by the SysCmd(7:5) bits.
Table 12-11 Encoding of SysCmd(7:5) for System Interface Commands
SysCmd(4:0) are specific to each type of request and are defined in each of
the following sections.
SysCmd(7:5) Command
0 Read Request
1 Read-With-Write-Forthcoming Request
2 Write Request
3 Null Request
4 Invalidate Request
5 Update Request
6 Intervention Request
7 Snoop Request
Request Type0 Request Specific
8 7 5 4 0