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212 L4400 User’s Guide
8 L4450A 64-Bit Digital I/O with Memory and Counter
You can also output the trace one sample at a time on the data lines using the
SOURce:DIGital:MEMory:STEP command. This command outputs one sample
and then puts the memory in the stopped state. The STEP command also
overrides the interrupt line so it can be used to trigger a transfer even if the
interrupt line is set to be the trigger source.
Deleting Traces
You can delete traces in memory to recover the memory space. Use the
TRACe:DELete:NAME command to delete a specific trace. Note that deleting a
specific trace does not de- fragment the memory. You can delete all traces using
the TRACe:DELete:ALL command.
Buffered (Memory) Input
Each bank on the L4450A has its own memory for use in buffered transfers.
Changing a bank from an output to an input will clear all memory for that
bank. The general steps to use input memory are:
1 Set the channel width and parameters.
2 Set the handshake mode.
3 Set the number of samples to collect.
4 Start the capture.
5 Check the status of the transfer.
6 Retrieve the captured data.
Set the channel width and direction. Use the CONFigure:DIGital command to
set the channel width, direction, thresholds, and polarity. See page 200 for
basic input operations.
Set the handshake mode. You must use synchronous handshaking mode.
Handshaking is described in more detail on page 203.
Set the number of samples to collect. The SENSe:DIGital:MEMory:SAMPle:COUNt
command sets the number of samples to capture. If you set the number of
counts to infinite (0 = default), the bank will capture data until a STOP is
received. Older samples are overwritten if memory gets full. Allowed sample
counts depend upon the channel width as follows:
• BYTE (8- bit) 1 to 65535
• WORD (16-bit) 1 to 65535
• LWORd (32- bit) 1 to 32767
Start the capture. The SENSe:DIGital:MEMory:STARt command sets the
channel to begin the data capture. The capture begins when the handshake
occurs.