Chapter 2 Using Your 653X
© National Instruments Corporation 2-9 653X User Manual
The state machine diagrams in Chapter3, Timing Diag rams, show more
precisely where this delay occurs in the handshaking sequence.
Choosing Continuous or Finite Data Transfer
You can transfer data indefinitely to/from computer memory or finitely by
specifying the number of points you want to transfer.
Finite Transfers
For finite transfers, the 653X device transfers the specified amount of data
to/from a computer memory buffer and stops the operation.
Continuous Input
For continuous input, the 653X device transfers input data to the computer
memory buffer continuously. As the device is filling the buffer, call the
DIG_DB_Transfer function or the DIO Read VI to retrieve the data.
Ifat any time the device runs out of space in the buffer, it pauses the
handshaking operation until your program clears up more buffer space.
You have the option to allow the device to continue acquiring data when it
runs out of buffer space and overwrite data you have not yet read. You can
specify this through the oldDataStop parameter in the DIG_DB_Config
function and the Data Overwrite/Regenerate parameter in the Digital
Buffer Control VI called by the DIO Start VI.
Continuous Output
Similarly, with continuous output, the 653X device continuously reads data
from computer memory. As the device retrieves data from the buffer, call
the DIG_DB_Transfer function or the DIO Write VI to write new data to
the buffer. The device will pause the handshaking operation if it runs out of
data to output. The data transfer will resume once more data is available.
500 2
600 1.66
700 1.43
PCLK Period in ns PCLK Frequency in MHz