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Comments 1. GENerator Digitizer Configuration. Both channels of the GENerator
digitizer are CONFigured for 10 readings on the 5V range. Thus, each block
of data generated is four bytes (two bytes/reading), followed by the
end-of-block (EOB) and end-of-frame (EOF) flags.
The GENerator digitizer’s trigger source is set to ECLT0. This VXI
backplane trigger line is controlled by the INSerter digitizer which feeds its
(internal) trigger signal to the GENerator digitizer. This causes both
digitizers to sample and transfer readings at approximately the same rate -
which is required for interleaved transfers.
Before setting the digitizer’s Local bus configuration, the Local bus chip is
reset. Next, the Local bus mode is set to GENerate and the feed (data
source) is set to CONVerter:BOTH. Finally, the interleaved transfer mode is
set. The number of readings per block is set to 2, and the end-of-block and
end-of-frame flags are sent after each set of readings. These settings are sent
as a single command string in order to prevent "Settings conflict" errors.
2. INSerter Digitizer Configuration. Like the GENerator digitizer, both
channels of the INSerter digitizer are CONFigured for 10 readings on the
5V range. Each block of data generated is four bytes (two bytes/reading),
followed by the end-of-block (EOB) flag.
The INSerter digitizer’s trigger source is its internal trigger. This trigger is
transferred to the GENerator digitizer over the VXI backplane ECLT0
trigger line. In this program the INSerter digitizer’s sample rate is set to 1
µs, thus, both digitizers sample and transfer readings at approximately a
1MHz rate.
For all digitizers in the interleaved transfer configuation, the Local bus chip
must be reset first. Next, the Local bus mode is set to INSert and the feed
(data source) is set to CONVerter:BOTH. Finally, the interleaved transfer
mode is set.
3. Digitizer Trigger Sources and Sample Rates. When doing interleaved
transfers over the Local bus, all digitizers must have the same trigger source
and the same sample rate. The maximum Local bus transfer rate is 80
MBytes/second which is equivalent to 40 MSamples/ second. The transfer
rate cannot exceed 40 MSamples/second regardless of the number of
digitizers.
4. Arming the Digitizers. In order for all digitizers to sample when a
trigger is received, the digitizers to the left of the rightmost digitizer are
armed (initiated) before the rightmost digitizer is triggered.
Appendix D Local Bus Interleaved Transfers 413