80KSBR200 Datasheet, PDF (25/172 Pages) Integrated Device Technology – sRIO SERIAL BUFFER FLOW-CONTROL DEVICE

IDT 80KSBR200
Notes
Advanced Datasheet*
4.0 Data Handling Within the SerB
The S-Port on SerB has the ability to act as an sRIO Endpoint or as an sRIO Bus Master. When the SerB is outputting
to an sRIO port, the queue holds the output packet routing information designating the final destination for the data.
In the PPS application, the SerB will typically act as an sRIO endpoint (slave), and will respond to commands received
through the PPS. In the event that there is an active waterlevel = watermark, the SerB shall become the sRIO bus master
to send the multicast packet to the PPS.
4.1 Inputting Data to the Queue
Incoming serial data must be directed to a queue upon entry into the SerB. The incoming packet data carries an identi-
fier that selects a "case scenario" for the data that includes the routing information. In sRIO, the source ID of the data
selects the "case scenario" for the data. This is designated at "Case Scenario Mode".
4.1.1 Command Input Buffer
There is an input buffer on the SerB that is capable of stacking a small number of commands. There is a separate
buffer for read and write commands. It should be noted that commands may become blocked by activity within a queue in
the SerB.
4.1.2 Output Buffer
There is an output buffer that is capable of stacking output packets on the SerB. In the event that multiple output
packets become stacked within the buffer, the higher priority packets will be sent first. A packet that is blocked on the bus
for any reason, will prevent the transmission of subsequent same priority packets and lower priority packets until the
blocked packet successfully sends, or is discarded.
4.1.3 Writing More Data than can Accept
Whenever an attempt is made to write more data to queue than there is space available to accept, the SerB will go
through the following stages:
◆ _{When the queue is full, a Full Flag will be set. The flag may then send any interrupts or doorbells to unmasked}
locations.
◆ _{The incoming data will be accepted in full packets and fill the input buffer on the FIFO port.}
◆ _{If the input buffer contains data that it cannot flush into the queue, the data will sit there, preventing the port}
from writing to the queue. Priority and maintenance packets will not be blocked, but data packets will be
blocked
◆ _{If the input buffer also overflows, the incoming packets will be rejected. Only full packets will be accepted. If}
there is not room to store a complete packet, the entire packet will be rejected. The sender will be notified of
the packet rejection.
◆ _{Once the full queue empties enough to allow the data in the input buffer to flow into the queue, the input buffer}
will again be free to accept more data.
Space Available
The Space Available flag is located in the Full Flag register. It is assumed that if multiple sources are writing to the
SerB, they will poll the space available register to see how much room is available for writing. When the space available
flag toggles, the flag will be sent to the destination ID within the register and to the port designated by the mask registers.
Any multicast will be the responsibility of the user.
4.2 Outputting Data from the Queues
The queue output is dedicated to a port and cannot be reconfigured. The queue is configured with a "Case Scenario"
that dictates a destination to which the data is sent. The sending of data is triggered by a waterlevel (event). The configu-
ration registers are used to set up the output mode.
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March 19, 2007
„2005 Integrated Device Technology, Inc. All rights reserved. Advanced Datasheet for informational purposes only. Product specifications subject to change without notice.NOT AN OFFER FOR SALE The information presented herein is subject to a
Non-Disclosure Agreement (NDA) and is for planning purposes only. Nothing contained in this presentation, whether verbal or written, is intended as, or shall have the effect of, a sale or an offer for sale that creates a contractual power of acceptance.