IDT88K8483 Integrated Device Technology, IDT88K8483 Datasheet - Page 54

• Manufacturer Part Number: IDT88K8483
• Description: Spi-4 Exchange Document Issue 1.0
• Manufacturer: Integrated Device Technology

PFP Ingress Flow Control for over booking mode
normal operation there are enough free segments, so the LIDs status are starving, and the SPI-4 ingress interface is sending starving status to the
adjacent device through the status bus. When the number of free segments for each LID is less than THR_STARV (for example 400 segments), the
LID status is changed to hungry, and the SPI-4 ingress interface starts sending hungry status to the adjacent device. When the number of free
segments for each LID is less than THR_HUNG (for example 300 segments), the LID status is changed to satisfied, and the SPI-4 ingress interface
starts sending satisfied status to the adjacent device. When the total number of free segments for all the LIDs is less than BUF_THR (for example 50
segments), the status of all the LIDs are changed to satisfied, and the SPI-4 ingress interface starts sending satisfied status to the adjacent device.
segments. In this case, the number of free segments for LID0 is less than THR_STARV (400), so LID0 sends hungry status to the adjacent device.
The number of free segments for LID1 is also less than THR_STARV (400), so LID1 sends hungry indication to the adjacent device.
segments. In this case, the number of free segments for LID0 is less than THR_HUNG (300), so LID0 sends satisfied status to the adjacent device.
The number of free segments for LID1 is also less than THR_HUNG (300), so LID1 sends satisfied indication to the adjacent device.
LID1 is 500, and the total number of free segments for both LID0 and LID1 is 12. In this case, the total number of free segments for both LID0 and
LID1 is less than BUF_THR (50), so LID0 and LID1 send satisfied status to the adjacent device.
IDT IDT88K8483
There are 4 main parameters for configuring the PFP ingress flow control for over booking mode:
- Maximum number of segments per LID is configured in M field in the
- Starving Free segments per LID is configured in THR_STARV field in the
- Hungry Free segments per LID is configured in THR_HUNG field in the
There are three status options per LID in the SPI-4 ingress PFP: starving hungry and satisfied. In SPI-4 ingress PFP for LP0/LP1 (for example), in
Detailed examples:
Example 1. LID0 gets data for 120 segments and LID2 gets data for 120 segments, so LID0 has 392 free segments and LID0 has 392 free
Example 2. LID0 gets data for 220 segments and LID1 gets data for 220 segments, so LID0 has 292 free segments and LID1 also has 292 free
Example 3. LID0 gets data for 250 segments and LID2 gets data for 250 segments, so the total number of occupied segments for both LID0 and
- Global Free segments per LID is configured in the BUF_THR field in the
Figure 22 PFP Flow Control Example For Over Booking Mode
PFP (508 segments, 127K bytes)
Hungry / Satisfied
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Starving
Satisfied
Hungry
PFP Buffer Segment Assign Table (p.
PFP Buffer Segment Assign Table (p.
PFP Buffer Management Configuration Register (p.
PFP Buffer Segment Assign Table (p.
Maximum Number Of Segments for LIDs 0 and 1 = 508
Global Free Segments for LIDs 0 and 1 = 50
Hungry Free Segments for LIDs 0 and 1 = 300
Starving Free Segments for LIDs 0 and 1 = 400
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October 20, 2006
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