IDT88K8483 Integrated Device Technology, IDT88K8483 Datasheet - Page 56

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

QDR-II Flow Control
IDT88K8483 can be configured to one of two different flow control modes using the EBP_EN field in the
(p. 123).
cation to the SPI-4 interface as shown in
pressure or occasional (emergency) backpressure (for example when egress is not rate limited).
pressure (for example rate limited egress).
satisfied or hungry, then the device sends satisfied status to the SPI-4 interface. If the QDR-II status is starving, then the device sends starving status
to the SPI-4 interface.
Flow Control Mode 1 - Packet Assembling
mode). In this option the PFP and the QDR-II should be programed to packet mode by setting to 1 the PKT_MODE field in the
Mode Control Registers (p. 123)
semble the interleave data from each channel to packet by monitoring the SOP and EOP indication. It starts the packet with the SOP indication and
ends the packet with the EOP indication. The device sends the data in packet mode from the QDR-II to the PFP and then to the port buffers and to the
SPI-4 interface.
PFP is used only as a temporary storage, so the packets should be sent immediately from the PFP. Therefore, there is not enough memory for sched-
uling too many packets, and there cannot be frequent back-pressure. If there is too many back pressure the storage space is limited, and the over-
booking mode is not efficient. Since in this case there is no much back-pressure, there is no need to transfer the back-pressure from the QDR-II to the
PFP and to the interface. Therefore, the IDT88K8483 sends the PFP status to the interface.
IDT IDT88K8483
The IDT88K8483 gets the QDR-II FIFO status information from the QDR-II interface, and the PFP LID status information from the PFP logic. The
If EBP_EN field in the
If EBP_EN field in the
- When the QDR-II flow control mode is mode 1, the device sends the PFP status to the SPI-4 interface.
- When the QDR-II flow control mode is mode 2, the device sends status to the SPI-4 interface based on the QDR-II status. If the QDR-II status is
In the packet assembling option the IDT88K8483 receives the data in interleaved mode and it sends the data in packet mode (non-interleave
An application example for flow control mode 1 (packet mode) is described in
According to the status information from the QDR-II FIFO and the PFP LID, and the flow control mode, the device generates the status indi-
PFP Egress Packet Mode Control Registers (p. 123)
PFP Egress Packet Mode Control Registers (p. 123)
and the PKT_MODE field in the
Table 3
QDR-II FIFO Status
SPI-4 Status Information (p. 56).
satisfied
satisfied
satisfied
starving
starving
starving
hungry
hungry
hungry
Table 3 SPI-4 Status Information
Auxiliary Packet Mode Configuration Register (p.
56 of 162
(Flow Control Option 2)
SPI-4 Interface Status
is 0 then the flow control mode is mode 1 - packet assembling, no back-
is 1 then the flow control mode is mode 2 - buffering, frequent back-
Figure
satisfied
satisfied
satisfied
satisfied
satisfied
satisfied
starving
starving
starving
24. In this example the device is in over-booking mode, the
PFP Egress Packet Mode Control Registers
131). In this case, the device reas-
October 20, 2006
PFP Egress Packet