Curtiss-Wright FHF5-PC4MWB04-00, Справочник по аппаратуре

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OPERATION
Copyright 2017 4-3 FibreXtreme Hardware Reference
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 propagated
to the remote Serial FPDP receiver, the pulse width from the host-bus interface must be
equal to or greater than the maximum Serial FPDP frame length (512 words of data with an
overhead of nine ordered sets). The use of these signals is host-specific and is explained
below for each SL100/SL240 product.
For SL100/SL240 PCI-based cards (PCI, PMC, and CPCI), the values of PIO1 and PIO2 are
retransmitted according to their received link values and the values of DIR and NRDY are
used as follows: if the receive interface is enabled, the values transmitted are the received
link values logically ORed with the PCI host-interface values; otherwise, the values are
retransmitted according to their received link values. The values of these four signals sent to
and received from the link are placed in the register set and then can be accessed by
software. These signals are typically used for application-dependent signaling between
nodes. The use of DIR and NRDY is consistent with the use of flow control (retransmission
of a STOP request) for loop operation. See the VITA 17.1 Serial FPDP specification for
additional details.
For SL100/SL240 CMC cards, the values of PIO1 and PIO2 are retransmitted according to
their received link values and the values of DIR and NRDY are used as follows: if the
receive interface is enabled, the values transmitted are the received link values logically
ORed with the FPDP host-interface values; otherwise, the values are retransmitted according
to their received link values. NRDY received from the link translates to /NRDY output from
the FPDP receiver (FPDP-RM or FPDP-R) port. Thus, reception of NRDY from the link
interface may be used to back off the FPDP transmitter, depending of the usage of /NRDY
used by the respective FPDP transmit master. Curtiss-Wright Controls’ SL100/SL240 CMC
cards, when functioning as a FPDP transmit master, will stop the transmission of FPDP data
when /NRDY is asserted by the FPDP receiver. The reception of a suspend request will
indirectly back off the FPDP transmitter, as the link logic no longer transmits link data, the
link Transmit FIFO will back up, which will eventually back off the FPDP transmitter via
the assertion of the /SUSPEND signal. The values of these four signals (PIO1, PIO2, DIR,
and NRDY) sent to and received from the link are placed on the FPDP bus and in the
register set, if applicable. If placed in the register set, they can be accessed by a
microcontroller via the optional microcontroller interface on the CMC carrier. The use of
DIR and NRDY is consistent with the use of flow control (retransmission of a STOP
request) for loop operation. See the VITA 17.1 Serial FPDP specification for additional
details.
Note that NRDY as a Serial FPDP signal has no direct impact on the operation of the link
logic. Rather, NRDY is passed through the link logic and its function is dependent on the
respective host interface. The Serial FPDP flow control (implemented via suspend requests
which are also known as STOP ordered sets) is used by the link logic and does not directly
affect the interface between the link logic and host interface.
NOTE
: One node on the loop MUST be in non-loop operation in order for loop operation
to work correctly. One node needs to remove the data from the loop. When switching
masters on the loop, both the previous master and the next master should be in non-loop
operation before the previous master switches into loop mode.