DAT

Requests a range of DMA buffer data points.

Mnemonic:

A/D DATa.

Syntax:

DAT $<$start, stop$>$

start: Starting index of DMA buffer (0-65535)

stop: Ending index of DMA buffer (0-65535). The value of stop must be equal to or greater than the value of start.

Return values:

Success:

A succession of values requested, in the form:

      DAT 1, pos, data
      DAT 1, pos, data
      ...
      DAT 1, pos, data

where pos is the word position of the data within the DMA buffer, and data is the data.

Failure:

DAT 0, err_msg

pos: The position in the data buffer that this data comes from. Ranges from start to stop, incremented by one every time a value is returned.

data: The requested data word for a given buffer position pos. This is a 16 bit, twos complement data word, with a scaling of 0.305 millivolt per bit.

err_msg: Should the command fail, this value will be an error message string, explaining the cause of failure. DAT may fail if:

• The wrong number of parameters were supplied.
• The parameters start or stop are non-numeric.

Remarks:

Setting the number of samples-per-cycle (see SFQ) and total cycles to integrate (see CYC) determines the total amount of 16-bit 2s complement samples taken by the A/D system and stored in the DMA buffer. The DAT command allows access to those samples. The samples returned lay between, and include, the start and the stop parameters. The A/D system always places the samples starting at position 0 of the DMA buffer. Since it is possible to specify start and stop values for any range within the DMA buffer, it is up to the client to ensure that the area of interest is currently active.

Example:

     send: DAT 0, 3
  receive: DAT 0, -1
           DAT 1, 0
           DAT 2, 5
           DAT 3, -6

See also
CYC, IFF, SEQ, SFQ