IDT88P8341 Integrated Device Technology, IDT88P8341 Datasheet - Page 27

• Manufacturer Part Number: IDT88P8341
• Description: Spi Exchange Spi-3 To Spi-4
• Manufacturer: Integrated Device Technology

SPI-4 egress data bursts
MAX_BURST_H or MAX_BURST_S parameter associated with each LID. For
a high priority (starving) LID the MAX_BURST_S parameter is used. For a low
priority (hungry) LID the MAX_BURST_H parameter is used. The PFP may
not fill the buffers to the level granted when a new segment needs to be used
in the SPI3-4 buffer memory or when the last fragment of a packet is copied into
the buffer. The information received over the FIFO status channel is interpreted
as status or credit information as selected by the CREDIT_EN flag in Table 78,
SPI-3 to SPI-4 flow control register (0x01). If the status mode is used, data will
be egressed until the status is changed. If the credit mode is used, the SPI-4
egress will issue only one credit’s worth data burst and then wait for another credit
from the status channel before issuing another LID burst.
SPI-4 egress FIFO status channel updates
status information for the LIDs associated to SPI-4 logical ports. The PFP
searches and selects a LID, fetches the associated information and queues data
to the SPI-4 egress. The obsolete buffer segment is returned to the free buffer
segment pool (unless the repeat test feature is enabled). Searching the LID to
be served is performed for both a high priority and a low priority LID. The priority
is defined by the status received from the SPI-4 egress module.
IDT88P8341 SPI EXCHANGE SPI-3 TO SPI-4
The PFP produces fragments of up to N*16 bytes. N is defined by the
The SPI-4 egress FIFO Status Channel Module continuously verifies the
[LP] = LID | EN | BRV
LID: Logical Identifier
EN: LID Enable
BRV: Bit Reversal
Figure 14. SPI-3 ingress LP to LID map
LID
27
SPI-3 ingress logical port mapping
Table 49) for the purpose of directing the packet fragments from the SPI-3 ingress
to its associated SPI-3 ingress main memory buffer segment pool. The SPI-3
LID map has 256 entries, one per SPI-3 LP, but only 64 LPs are supported on
the SPI-3 interface at any one time. The SPI-3 interface has an enable bit, as
well as the ability to reverse the bit ordering within bytes of the interface. The
packet fragment length is associated with the SPI-3 interface. The allowed range
is 0 to 255 bytes per packet fragment. The last fragment of a packet can be shorter
than the programmed fragment size. The SPI-3 port can be independently set
for either Link or PHY mode of operation.
SPI-3 ingress LID associated control
and maximum packet length. The minimum packet length can be set from 0 to
255 bytes in one byte increments. The maximum packet length can be set from
0 to 16,383 bytes in one byte increments. Each LID can be enabled and disabled
independently.
The SPI-3 interface has an associated SPI-3 ingress LP to LID map, (See
Each LID on the SPI-3 interface has the ability to be programmed for minimum
EN
BRV
INDUSTRIAL TEMPERATURE RANGE
256 LPs
6372 drw15
APRIL 10, 2006