Agilent Technologies L4400 User Manual
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L4400 User’s Guide
8
L4450A 64-Bit Digital I/O with Memory and Counter
You can set a channel to output in either active drive or open collector
configurations. When set to
ACTive
, the module drives the digital lines for
both high and low. The voltage level that represents a logic ‘1’ can be set
using the
SOURce:DIGital:LEVel
command. Output voltages can range
from 1.66 V (default) to 5 V.
When the channel is set to
OCOLlector
, lines are driven low, but set to
high impedance (Hi- Z) when asserted. In the open collector mode, multiple
lines can be connected together by providing external pull- ups.
Once a channel has been configured, write digital data to the channel
using the
SOURce:DIGital:DATA
command.
SOUR:DIG:DATA:LWOR 26503,(@1201)
You may also use a hexadecimal format to represent values in the
commands. For example, to send the decimal value of 26503 in hex use
the command form:
SOUR:DIG:DATA:LWOR #h6787,(@1201)
Note that the data should match the channel width configured using
CONFigure:DIGital:DATA:WIDTh
command. The data written is masked
by the configured width so that any extra bytes will be discarded.
For example: sending the value 65531 to a byte wide channel will result
in the channel discarding the upper byte and outputting 251.
Channel Width and Polarity, Threshold, Level, and Drive
When the width of a channel is set to
WORD
or
LWORd
, the channel
direction (input or output) of the channels spanned by the width is
controlled by the channel in operation. That is, all grouped channels are
automatically set to the same input or output operation.
Channel settings of polarity, threshold, level, and drive mode are
unchanged when channels are combined. For example, consider the
following command sequence.
CONF:DIG:POL NORM,(@1101)
CONF:DIG:POL INV,(@1102)
CONF:DIG:WIDT WORD,(@1101)
N O T E
When using external pull-ups in the open collector mode, the outputs
will not exceed 5 V.
N O T E
Writing to a channel automatically configures the channel as an output.