Curtiss-Wright FHK4-FM4MWB04-00, Справочник по аппаратуре

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OPERATION
Copyright 2012 4-2 FibreXtreme HW Reference for FPDP Cards
All FPDP signals, with the exclusion of /SYNC, are passed around the Receive FIFO
and are not synchronized with the data stream.
4.2.2 Transmit Operation
The transmit operation first has to collect data in the Transmit FIFO for transmission.
FPDP cards collect any data words accompanied by /DVALID on the FPDP interface.
Once a data word is in the FIFO, transmission can begin. The framing state machine first
checks that there is no data in the Retransmit FIFO and that the remote node is not
telling this node to back off. If it is clear to send, after it transmits the next SOF it begins
filling the data frame as full as possible (up to 2048 bytes). The data is then encoded and
sent out across the link. If there is data in the Retransmit FIFO or the card is being
backed off from the destination, then the card waits until both conditions are clear before
it starts transmission. Note that SYNC and SWDV can also be transmitted by the link
logic and these two types of synchronization primitives are handled by the Transmit
FIFO and transmit control logic in a similar method as standard data. Specifically, they
are written to the link logic through the same interface, passed through the same internal
link logic path, and are used in the assembly of link frames in a similar fashion, although
the maximum frame size does differ for these types of associated Serial FPDP frames.
All FPDP signals, with the exclusion of /SYNC, are passed around the Transmit FIFO
and are not synchronized with the data stream. For PCI variations of this card, the FPDP
signals can be written to a register and then transmitted across the link.
4.2.3 Loop Operation
In the Loop Operation discussion below, SL100/SL240 is used generically to refer to
any Curtiss-Wright Controls SL100/SL240 card. Anything that applies to only a specific
SL100/SL240 product will be noted as such.
Loop operation with the SL100/SL240 acts like a virtual FPDP bus where one source
(the loop master) can transmit to any number of receive nodes. The link protocol is the
same for this operation, except any node in the loop may assert a suspend request
embedded in this data stream. This implies if one node on the loop is not ready to
receive data, the source is backed off for all nodes. This is the same way that multi-drop
FPDP busses function.
The fundamental difference between a loop master and a receiving node is the loop
master does not have its loop retransmission enabled. So, to the loop master, it appears
as if it is still in a point-to-point connection with a single node. Receiving nodes, on the
other hand, have knowledge that they are in a loop configuration and must be configured
as such. Note that the loop master receives all the data it transmits, so data can either be
checked for errors or ignored when it is received. This checking (beyond verification of
CRC and 8B/10B decoding validity) is not done in the SL100/SL240 and must be
implemented by the system designer.
The receivers on the loop can choose to collect the data or ignore it off the loop. If the
Receive FIFO is enabled (the node is collecting data), a suspend request may be asserted
by this node as the data passes through. If it is not configured to receive the data, it
simply passes the data through the Retransmit FIFO without modifying the suspend
request.
Serial FPDP supports the DIR, NRDY, PIO1, and PIO2 FPDP signals. These signals do
not propagate through the Transmit FIFO or the Receive FIFO and thus cannot be
directly associated with the corresponding data. To guarantee a pulse on these signals is