Reminder Needed for SPI-3

Gene_Milligan at notes.seagate.com Gene_Milligan at notes.seagate.com
Mon Oct 4 13:45:47 PDT 1999


* From the T10 Reflector (t10 at t10.org), posted by:
* Gene_Milligan at notes.seagate.com
*
A change was made to the SCSI bus data & information phase DT timing values
table to the ATN Receive Setup Time that is not self evident from the other
specifications. It appears that some additional factor has been applied to
this signal that is not applied to data signals. Another possibility is
that the change contemplated a different point to measure the ATN Receive
Setup Time than the device connector as is specified.

The original intent was to provide a somewhat arbitrary 10 ns additional
setup time for ATN Receive Setup Time. If the Signal Timing Skew (cable
assembly skew plus ISI) were subtracted from the ATN Transmit Setup Time,
10 ns would result for each negotiated timing range. The additional setup
time is appropriate to allow non precision etch layout, bond outs, and
logic for the ATN signal. The specified ATN Receive Setup Time may be
adequate but its budget is a mystery compared to data signals that either
in random or potential worse case conditions should have the same
distortion conditions from transmitting device connector to receiving
device connector.

Gene



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