80KSBR200 Datasheet, PDF (31/172 Pages) Integrated Device Technology – sRIO SERIAL BUFFER FLOW-CONTROL DEVICE

IDT 80KSBR200
Notes
Advanced Datasheet*
4.8 Packet Tally Indicator
In cases where the SerB bursts data to one of the DSPs, the DSP has no way of knowing that it has received the data.
The SerB has the ability to send a doorbell indicating that the designated (programmed) number of packets has been sent,
so that DSP may act.
Bursting must be done on frame boundaries within the DSP/PPS application so that the DSP receives the doorbell on
the frame boundary. In PPS, messages may be passed more quickly than data packets, so the message may arrive prior
to the data. To avoid this, the DSP must decide what the delay is through the system for each (data and message). The
DSP may then program an offset into the SerB registers and a frame size.
The TI DSP has no ability to analyze the contents of a doorbell, but instead uses 6 bits of the 16 bit data field as a
pointer to an interrupt. The pointer is fixed in the DSP, meaning that the pointer must be programmable in the SerB to
match the pointer required by the DSP.
Relating this to the SerB, the "case scenario" is used to identify the DSP as a target. Every time a "case scenario" is
accessed, the counter within the case scenario shall increment. When the count reaches the maximum programmed for
that case, the SerB shall send a doorbell to the destination ID designated in the case scenario, and the count shall reset.
The flag register may be used, except the doorbell must be sent regardless of whether previous flags have cleared.
Regarding the "offset", aside from initial power up/reset, it is uncertain what the trigger event is that would require an
offset. Therefore, the SerB shall provide an offset to the first frame count after power up and upon any reset that clears
data. Since the offset is contained in the case scenario, it may be accessed at any time by any of the programming sources
and can be adjusted as needed.
The "Packet Tally Indicator" Frame Size, Frame Offset, Count, and whether to send a doorbell are contained in each
case scenario.
4.9 Packet Interval Timer
The PPS and potentially other devices may not have the ability to accept data at an accelerated rate. The PPS
processes incoming data as it arrives, limiting the amount of data that can be accepted in a burst. To solve the problem, a
"Packet Interval Timer" has been added to the SerB to regulate the spacing between packets going out the port. There is a
separate programmable timer for data packets and priority packets, since they take different routes through the PPS.
Every time a packet is sent, the timer is reset and then counts down. Another packet of the same type may not be sent until
the timer times out.
4.10 Protocol Translation
Through the sRIO port on the SerB, data may be written to or read from the FIFO. The port also has the capability of
initiating data transfers (as a master), and writing data out of the port to another location. In addition, SerB control words
may be written into the SerB through the port to configure or to read the status of the device.
When using the SerB in two sRIO domains, translation issues arise. It should be noted that the SerB has limited trans-
lation capability. Its primary translation function is receiving data, storing data, and subsequently transmitting the data. The
ability to pass commands through the SerB is limited. To insure compatibility, there are constraints upon the data. The
SerB will handle all link maintenance functions, required responses, retransmissions, and other negotiations.
In the PPS application, the SerB is essentially an sRIO to sRIO translator. The SerB receives data in packet form,
stores it, and then transmits it at the designated time on the same port. The incoming packet must match the outgoing
packet in size. PPS uses only a designated (programmed) packet size.
31 of 172
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.