Sun Microsystems UltraSPARC-I User Manual page 133

raSPARC User's Manual
4
3
0
Cycle 1
Figure 7-22 P_REPLY Packet Format (Cycle 2 not present in all P_REPLYs)
P_REPLYs take either one or two interconnect clock cycles. The first cycle con-
tains the P_REPLY type, and the Class bit. The second cycle, if present, contains
the Master ID (MID) of the UltraSPARC that generated the original request.
Table 7-17 shows the P_REPLY encodings and the number of cycles in each pack-
et.
Table 7-17 P_REPLY Encoding
Type Cycles
DLE 1 Idle
FERR 1 Fatal Error
RERR 2 Read Data Error
SNACK 2 Coherent S_REQ Non Existent ACK
RAS 2 Read ACK Single
SACK 2 Coherent S_REQ ACK
AK 2 Interrupt Acknowledge
SACKD 2 Coherent S_REQ Dirty Victim ACK
The Class values are indicated as follows:
•
0=hardwired to 0
•
X=don't care
•
C=Copied from the P_REQ packet
With the exception of P_FERR, UltraSPARC generates all P_REPLYs as an ac-
knowledgment to a previous SC request. UltraSPARC can assert P_FERR at any
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time to indicate a fatal error requiring system reset. upon seeing P_FERR from
Class
Type
Name
4
Master ID (MID)
0
Cycle 2
Reply to Transaction
Default State
All transactions, any time
P_NCBRD_REQ
S_REQ
P_NCRD_REQ
S_REQ
P_INT_REQ
S_REQ
Class Type
0 0000
X 0100
C 0101
C 0111
C 1000
C 1010
C 1100
C 1101