VXI Technology, Inc.
26
VM1548C Programming
I
NPUT
R
EGISTER
C
IRCUIT
This section refers to the bi-directional port when configured as an input. The SCPI command
used to configure a port as an input is:
SOURce:DATA:ENABle <port #> OFF
The port is programmable to allow the data to be transparent or clocked. If the port is clocked,
there are several choices for the clock source. The method for selecting clocked mode and the
source of the clock is done with one SCPI command.
INPut:REGister:SOURce <port #> <source>
Where <port> is 1 of 6 data
registers and <source> is
EXTERNAL, TTLTRIG, GLOBAL
(TRIGOUT) or IMMEDIATE
Regardless of the port’s input mode, note that data inputs to the module do not contain pull-up or
down-biasing resistors. As such, if the user does not provide either active or passive biasing of the
data inputs, a read of the port may result in either a “1” or a “0” being read from the data inputs.
The method for selecting transparent mode is:
INPut:REGister:SOURce <port #> NONE
Where <port> is 1 of 6 data
registers and NONE means this
data register is transparent
EXAMPLES
The following SCPI commands will clock the data in on port #3 using the IMMEDIATE pulse.
SOURce:DATA:ENABle 3 OFF
INPut:REGister:SOURce 3 IMMEDIATE
TRIGger:SEQuence:IMMediate
This provides a rising edge clock
FORMat ASCII
READ? 3
Example of read value is 255
The following is an example of reading from a port operating in transparent mode. This method
requires no clock edge for the data to be available.
SOURce:DATA:ENABle 5 OFF
INPut:REGister:SOURce 5 NONE
FORMat BINARY
Example of read value is
#B11111111
READ? 5
The data presented on the external
connector is what will be read
The following example selects the external CLK3 line to clock the data port. In this example, it is
assumed the external CLK3 signal is a steady logic low and the clock edge is produced by
toggling the clock polarity.
SOURce:DATA:ENABle 3 OFF
INPut:REGister:SOURce 3 EXTERNAL
INPut:REGister:POLarity 3 NORMAL
INPut:REGister:POLarity 3 INVERT
This provides a rising edge clock
FORMat HEX
READ? 3
Example of read value is #HFF
Содержание VM1548C
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