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4. Internal Switching Fabric > Packet Queuing
90
Tsi574 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
4.4.1.1
Egress Watermark
The ISF egress arbiter generates flow control for a given priority of traffic based on
watermarks
.
Watermarks are defined for priority 0, 1, and 2 packets (no watermark is defined for priority 3 packets
because they are always accepted whenever there are free buffers). The watermark values are
programmable and are located in
“RapidIO Port x ISF Watermarks” on page 385
Rules for Programming Watermarks
The following rules are applied to Tsi574 watermarks:
•
No watermark is associated with Priority 3 packets
•
A priority
x
packet is accepted in the buffer if the number of free buffers is greater than the
programmed watermark of the associated priority. For example, when the PRIO1WM field is
programmed to three, a priority 1 packet is accepted only when there are four or more free buffers.
•
The three programmed watermarks (PRIO0WM, PRIO1WM, and PRIO2WM) must contain
values where PRIO0WM > PRIO1WM > PRIO2WM > 0 at all times.
•
The watermarks for the three priorities must allow for the following minimum levels:
— PRIO2WM >= 1
— PRIO1WM >= 2
— PRIO0WM >= 3
The hierarchy of watermarks ensures that packets of lower priority can never consume all buffers and
prevent packets of higher priority from being transmitted. With the correct setting of the watermarks,
there is at least one priority 3 packet in a full buffer (that is, if all buffers are filled, then at least one of
the buffers must be occupied by a priority 3 packet).
Violating any one of the watermark rules creates a deadlock situation in the system.
Содержание IDT Tsi574
Страница 1: ...IDT Tsi574 Serial RapidIO Switch User Manual June 6 2016 Titl...
Страница 20: ...About this Document 20 Tsi574 User Manual June 6 2016 Integrated Device Technology www idt com...
Страница 34: ...1 Functional Overview JTAG Interface 34 Tsi574 User Manual June 6 2016 Integrated Device Technology www idt com...
Страница 100: ...4 Internal Switching Fabric Packet Queuing 100 Tsi574 User Manual June 6 2016 Integrated Device Technology www idt com...
Страница 224: ...11 Signals Pinlist and Ballmap 224 Tsi574 User Manual June 6 2016 Integrated Device Technology www idt com...
Страница 490: ...B Clocking P_CLK Programming 490 Tsi574 User Manual June 6 2016 Integrated Device Technology www idt com...
Страница 512: ...Index 512 Tsi574 User Manual June 6 2016 Integrated Device Technology www idt com...