80ksbr200 Integrated Device Technology, 80ksbr200 Datasheet - Page 28

• Manufacturer Part Number: 80ksbr200
• Description: Srio Serial Buffer Flow-control Device
• Manufacturer: Integrated Device Technology

„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.
IDT 80KSBR200
Notes
4.6 Waterlevel and Watermarks
term "waterlevel" refers to the actual data level within a queue, regardless of whether a "watermark" is used. When the
waterlevel in the queue reaches the watermark, an event will take place, depending upon the configuration. The waterlevel
and watermarks are used primarily as an indicator to control data flow within a queue.
space (1/256th of the queue total) and do not deal with actual data counts. Waterlevels actually count packets or bytes as
designated.
4.6.1 Waterlevel Controls
waterlevels:
still possible to receive write commands on the queue input.
4.6.2 Example Uses of Waterlevels
Stable Data Level in Queue
until the data level reaches the watermark. Upon the waterlevel reaching the watermark, for every packet received, the
queue will transmit an equivalent data item. The following items set up this scenario:
PPS Specific Use of this Scenario
output packets. The delay is dependent upon the system requirements, but once the system is configured, it remains fixed.
It could be any designated delay, but the maximum in the TI DSP application is 10ms. The quantity of packets that would
accumulate within the designated time frame would be dependent upon how many RF cards are used in the basestation.
quantity of packets, a time interval can be derived from the total. Using the watermark to trigger packet transmissions, the
SerB may be used as a programmed packet delay.
reform packets to all be equal in size regardless of the number of antennas, but in some (rare) PPS applications that have
multiple antennas, it may be possible for the PPS to send packets of various sizes to the SerB. This should cause no prob-
In the SerB, the "watermark" is a programmable event trigger threshold for the data level associated with a queue. The
The waterlevels are different than the PAF and PAE flags, because PAE/PAF flags deal in increments of total memory
Waterlevels are primarily controlled in the configuration registers. The following items are available for controlling the
It should be noted that when operating as a waterlevel master, the "master mode" only affects the queue output. It is
There are several possible uses of waterlevels and watermarks. A few of the suggested applications are as follows.
This application allows the steady maintenance of a data level in a queue. As data is received, it is stored in the queue
The basestation application that uses the PPS requires that there be a specific timed delay between the SerB input and
The PPS issues packets to the SerB on a stable time interval, meaning that by using the watermark to designate a
In the typical PPS application, all packets will be identical in length and at equal time intervals. Usually the PPS will
Data in queue is held in packets.
Waterlevel - A counter that holds the actual data level in a queue. The count will be in packets.
Watermark - This word holds the trigger point for the waterlevel. When the waterlevel reaches this point, the
flag will be set. The flag may cause other events to occur (doorbells, interrupts, etc.)
A single packet at a time will be sent in their original sizes. Packets will continue to be sent, until the waterlevel
drops below the watermark. The remaining data will be held in the queue.
Space Available - This is a word in the waterlevel register that indicates how much space is remaining in the
queue. The space is in packets. The value of the counter is the total capacity of the queue minus the number
of bytes already consumed.
The queue is set up to be a master
The waterlevel is programmed to count packets
The watermark is set to the desired number of packets to be held within the queue at all times
The queue sits idle when the packet within the queue is less than the watermark. Packets are received, but
not transmitted
If the waterlevel reaches or exceeds the watermark, the queue will transmit enough packets to bring the
waterlevel back below the watermark.
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Advanced Datasheet*
March 19, 2007