IBM PowerPRS Q-64G
Packet Routing Switch
Preliminary
Table 3-11. Egress Idle Packet, Byte H0 Field Descriptions
Bit(s)
Field Name
Description
Identifies the type of grants carried in byte H1 of the packet header:
0
1
Subport grants (default value)
Multicast grants (set to ‘1’ every 61 packet cycles or when the multicast grant status
changes)
The default value is ‘0’. In this case, the set of subport grants carried by the egress idle packet is
determined by the subport grant type/priority flywheel and the subport grant port flywheel. The
FC byte carries the status of these flywheels (see Tables 3-18 and 3-19).
Every 61 packet cycles, multicast grants are sent in place of the subport grants. Multicast grants are
also sent immediately when the multicast grant status changes. The grant type/priority and subport
grant port flywheels are incremented even when the multicast grants are inserted in place of the
subport grants.
Grant Type
(high channel)
0
Note: A subport multicast grant is the logical AND of the individual subport multicast grants that
were received in ingress packets for all the ports in the range (see Section 3.6 Subport Flow Control
on page 53).
Reports the status of the extended output queue grant flywheel:
256-Gbps Configuration
512-Gbps Configuration
Extended Output Queue
Grant Flywheel Status
(low channel)
0
1
Ports 0 to 7
Ports 8 to 15
0
1
Ports 0 to 15
Ports 16 to 31
See Section 3.3.6.1 Extended Output Queue Grant Flywheel on page 37 for more information.
1
Parity
Header parity.
2:3
Protection
Must be set to ‘00’ for idle packets.
Identifies the packet color for switchover support. See the ingress idle packet color field description
in Table 3-2.
4:5
6:7
Color
Reports the status of the output queue grant priority flywheel:
00
Priority 0
Priority 1
Priority 2
Priority 3
Output Queue Grant 01
Priority Flywheel Status 10
11
See Section 3.3.6.2 Output Queue Grant Priority Flywheel on page 37 for more information.
Functional Description
Page 40 of 199
prsq-64g.01.fm
December 20, 2001
IBM [ IBM ]
