Sun Microsystems UltraSPARC-I - Page 106

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7. UltraSPARC External Interfaces
Figure 7-15 Arbitration: SC Arbitrates and Sends a Packet to Port
0
Figure 7-16 shows the timing when the SC relinquishes ownership after is has
driven a request packet. Port
0
asserts its request and is allowed to drive its pack-
et(s) after one dead cycle.
Figure 7-16 Arbitration: SC Gives Up Ownership to Port
0
In Figure 7-17, Port
1
encounters a quiescent bus when asserts its request. It is al-
lowed to drive its packet(s) after one arbitration cycle.
Figure 7-17 Arbitration: Bus Quiescent—Port
1
Becomes CURRENT DRIVER
000 00
SC drives
SYSADDR &
Addr_Valid<0>
Undriven
Addr_Valid<0>
SYSADDR &
Port
0
drives
LAST PORT DRIVER
Req<0>
SC Request
SYSADDR
Addr_Valid<0>
Addr_Valid<0>
Cycle 0 Cycle 1
Cycle 0 Cycle 1
000 00
Port
0
owner
DrivesDrives
SC owner,
LAST PORT DRIVER
Req<0>
SC Request
SYSADDR
Addr_Valid<0>
Addr_Valid<0>Addr_Valid<0>
Cycle 0 Cycle 1
Cycle 0 Cycle 1
000 11
Request
Asserted
Arbitration
Occurs
First Cycle
of Packet
LAST PORT DRIVER
Req<0>
Req<1>
SYSADDR
Cycle 0 Cycle 1
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