Serial Instrument on ASRL

An instrument connected to an RS-232 COM port on a local PC is a serial instrument. (To add instruments connected to an RS-232 COM port on a LAN gateway or another PC acting as a remote I/O server, refer to Remote Serial Instrument settings.). The VISA identifier ASRL<n> identifies the serial interface on which the instrument resides. Typically, one interface for each serial port (COM port) is available on a PC. For example, ASRL3 identifies the port known to Windows as COM3.

Notes:

  • Serial instruments are not auto-discovered, so you must add them manually. For more details, refer to Instrument Discovery and Identification on Specific Interface.
  • The instrument's settings must match the serial interface's settings. Making changes to the interface properties does not change the settings on the serial instrument.

Serial Instrument Properties

Property Description
Test Station

The Select Test Station(s) dropdown shows the connected test station. Currently, it is not functional and a placeholder for future releases.
VISA Interface ID A name used by VISA and Keysight software to uniquely identify this interface. For a serial interface, the VISA interface ID is of the form ASRLn, where n is an integer typically corresponding to the serial port number to which the instrument is connected: for example, ASRL3 for serial port COM3.
Baud Rate

The Baud Rate refers to the speed of data transmission and reception on the RS-232 serial interface. The appropriate baud rate selection depends upon the instrument connected to the serial port. Refer to the documentation accompanying your peripheral device for guidance on configuring this value.

default value: 9600

Valid Values: 50, 75, 110, 134, 150, 300, 1200, 2400, 3600, 4800, 9600, 19200, 38400, 57600, 76800, 96000, 115200, 134400, 172800, 211200, 230400, 460800, 921600
Data Size

Data Bits represent the number of bits within a character frame in RS-232 serial data transmission. The appropriate data size selection is contingent upon the peripheral device (instrument) connected to the serial port. Consult the documentation for your instrument to configure this value.

default value: 8

Valid Values: 5, 6, 7, 8
Flow Control

Flow Control refers to the protocol employed to regulate data transmission over the RS-232 serial connection. The appropriate flow control selection is determined by the peripheral device connected to the serial port. Refer to the documentation for your peripheral device to configure this value.

default value: "NONE"

Valid Values: "NONE", "XON/XOFF", "RTS/CTS", "DTR/DSR"

VISA supports the combinations "RTS/CTS AND XON/XOFF" and ""DTR/DSR AND XON/XOFF" for the serial interface's flow control property, but there is not a way to set those states in Keysight software. Both hardware and software flow control can be enabled simultaneously in code. Refer to the Keysight VISA Help page on ASRL Flow Control Combinations for additional information.

Stop Bits

Stop Bits refer to the number of bits utilized to signify the end of a character frame in RS-232 serial data transmission. The appropriate selection of stop bits is determined by the peripheral device connected to the serial port. Consult the documentation for your peripheral device to configure this value.

default value: 1

Valid Values: 1, 2
Parity

RS-232 serial hardware uses parity to validate data transmission. The choice of parity value depends upon the peripheral device connected to the serial port. Refer to the documentation for your peripheral device to configure this value.

default value: "NONE"

Valid Values: "NONE", "ODD", "EVEN", "MARK", "SPACE"
SRQ Line

The SRQ Line represents the modem status line on the serial interface, monitored for Service ReQuests (SRQs). Options include RI (Ring Indicator), CTS (Clear To Send), DSR (Data Set Ready), and DCD (Data Carrier Detect).

Certain instruments can request service from the controller, known as an SRQ (Service ReQuest). On the IEEE-488 GPIB bus, an SRQ notifies the controller that the instrument requires service.

The SRQ Line value is employed to choose one of the four RS-232 status lines for SRQ events. When this line toggles, any handlers installed for this interface with the ionsrq SICL function will be activated. The default SRQ Line is the Ring Indicator (RI) line.

default value: "RI"

Valid Values: Readonly, always with the value of "RI"
Auto-identify This Instrument When this check box is selected, an *IDN? Query is sent to the instrument periodically. When this check box is cleared, this instrument is excluded from periodic identifications.