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SPI-4.2 Lite v4.3 User Guide www.xilinx.com 73
UG181 June 27, 2008
Sink Core
R
Figure 4-16 illustrates back-to-back short packets. In this example there are four channels
that are each sending 17-byte packets with a maximum burst of 16 bytes.
Sink FIFO Burst Error
When data received on RDat is terminated on a non-credit boundary without an EOP, the
Sink core flags this error at the end of the burst by asserting SnkFFBurstErr.
SnkFFBurstErr may be used by the user logic to indicate missing EOPs, or incorrectly
terminated bursts. In this case the Sink core does not assert SnkFFEOP or SnkFFErr.
EOP Abort Handling
When an EOP abort is received, the Sink core asserts the output flags SnkFFEOP and
SnkFFErr when the packet is terminated. In this case, the Sink core does not assert
SnkFFBurstErr.
Loss of RDClk
When RDClk is not driven, the status signal DCMLost_RDClk is asserted. If RDClk is
never present, then the Locked_RDClk signal will never be asserted and the Sink core will
not achieve synchronization. If RDClk is present and then lost, then Locked_RDClk will
be deasserted and DCMLost_RDClk will be asserted. If DCMLost_RDClk is asserted, it is
recommended that you reset the Sink core and re-initiate the synchronization process.
Sink SPI-4.2 Bus Error and Sink Bus Error Status[7:0]
A Sink SPI-4.2 Bus Error (SnkBusErr) is an error indication of SPI-4.2 protocol violations
or bus errors not associated with a particular data packet. Sink Bus Error Status
(SnkBusErrStat[7:0]) triggers simultaneously with SnkBusErr and clarifies which
protocol violations have occurred. Each bit of the SnkBusErrStat bus corresponds to one
of the following detected conditions.
• SnkBusErrStat[0]: Minimum SOP spacing was violated
• SnkBusErrStat[1]: EOP control word not immediately preceded by data
(Example: EOP followed immediately by another EOP)
• SnkBusErrStat[2]: Payload control word not immediately followed by data
(Example: A payload control word is followed immediately by another payload
control word.)
• SnkBusErrStat[3]: DIP4 error received during idle or training patterns
• SnkBusErrStat[4]: Reserved control words received
Figure 4-16: Short Packet Support
CH 0
16 bytes
1 byte w/ EOP
CH 1
CH 2
CH 3
Ch 0
CTL
16 bytes
Ch 1
CTL
16 bytes
Ch 2
CTL
16 bytes
Ch 3
CTL
16 bytes
Ch 0
CTL
1 byte
Ch0 EOP
Ch1 CTL
1 byte