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L4450A 64-Bit Digital I/O with Memory and Counter 8
L4400 User’s Guide 213
Check the status of the transfer. You can use the
SENSe:DIGital:MEMory:DATA:POINts?
query to return the number of
samples currently in memory.
Retrieve the captured data. Set the desired memory retrieval format using the
SENSe:DIGital:DATA:FORMat command. You can set the memory to be read
as either LIST or BLOCk. The LIST parameter (default) returns the data as
comma separated ASCII values. BLOCk returns the data in IEEE- 488 block
format.
Before you can read the data in memory, you must stop the memory
operations using the
SENSe:DIGital:MEMory:ENABle OFF command.
Read all the captured data using the
SENSe:DIGital:MEMory:DATA:ALL?
query. This performs a non- destructive read of all data in the bank’s memory.
To read specific captures, use the
SENSe:DIGital:MEMory:DATA? form of the
command. This command takes index and count parameters to specify which
data to retrieve. The oldest data in memory has an index of ‘0’. The count
specifies the number of samples to read. count + index must be less than the
number of captured points.
Both these data reads are non-destructive to the bank memory. To clear the
memory for new data, send the
SENSe:DIGital:MEMory:CLEar command.
Interrupt Lines
Each bank has an interrupt line that can be used with memory input or output
operations. When a bank is set to input data, the interrupt line is an output.
When a bank is set to output data, the interrupt line is set to be an input. You
can set the polarity of the interrupt line for input and output operations using
the
CONFigure:DIGital:INTerrupt:POLarity command.
You can configure the interrupt line drive mode, output drive level, and input
threshold. These parameters are set for both the handshake lines and
interrupt line on a bank. See page 204 for details about setting these
parameters.
Memory Output Operations
For memory output operations, the interrupt line is sensed and can be used to
start or stop memory output operations. This provides a hardware means to
control the data output.
The
SOURce:DIGital:INTerrupt:MODE command sets how the bank will
behave when using memory output. The mode can be set to one of three values:
• STARt: The memory output will begin on the rising edge of the interrupt
line.