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Appendix D
Local Bus Interleaved Transfers
Appendix Contents
This appendix contains information on interleaved data transfers using the
HP E1429B and the Local bus.
Interleaved
Transfers
In an interleaved transfer, multiple digitizers transfer one reading or one set
of readings (both channels) per block. The leftmost digitizer is set to the
GENerate mode and the inner digitizer(s) is set to the INSert mode. A
device such as the HP E1488 memory card is usually the consumer.
Readings are taken directly from the digitizer A/Ds.
As an example, the transfer sequence from digitizers D
1
- D
3
, where D
1
is
in generator mode (leftmost slot) and D
2
and D
3
(rightmost slot) are in
insert mode would appear as:
EOF EOB D
1
EOB D
2
EOB D
3
----->consumer
where EOF is the end-of-frame flag, EOB is the end-of-block flag, and D
n
is either a two byte (one channel) or four byte (two channel) reading.
Note If you are using the interleaved transfer mode of the HP E1429B with the
HP E1485 Digital Signal Processor module, note that the E1485 can accept
no more than 256 blocks.
Maximum Data
Transfer Rate
The maximum data transfer rate over the Local bus is 80 MBytes/second
which is equivalent to 40 MSamples/second. The HP E1429B digitizer
transfers data at 40 MSamples/second when readings are taken on two
digitizer channels at the maximum sample rate of 20 MHz.
When doing interleaved transfers, the transfer rate cannot exceed
40 MSamples/second, regardless of the number of digitizers used. The
maximum sample (transfer) rate allowed is determined by:
40 MSamples / number of channels
Appendix D Local Bus Interleaved Transfers 405