Appendix D

Local Bus Interleaved Transfers

Appendix Contents

Interleaved Transfers

This appendix contains information on interleaved data transfers using the HP E1429B and the Local bus.

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 D1 - D3, where D1 is in generator mode (leftmost slot) and D2 and D3 (rightmost slot) are in insert mode would appear as:

EOF EOB D1 EOB D2 EOB D3 ----->consumer

where EOF is the end-of-frame flag, EOB is the end-of-block flag, and Dn 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 The maximum data transfer rate over the Local bus is 80 MBytes/second Transfer Rate 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

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HP E1429A manual Local Bus Interleaved Transfers