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5. Digital Operation
Instrument States
The HVG-2020A will be in one of the following states as reported by the SS command:
State 4
State 8
After power up, the instrument will enter the Operation state (4); this is indicated by the Status LED
being solid green
The Calibration state (8) is used to adjust the Analog Output hardware using the TDAO, TDAS, TDAZ and
TOFF commands. This state is entered by sending the SS8 command and exited by sending the SS4
command.
Serial Communications
5.2.1. General
The HVG-2020A provides three ports for serial communication: a 3.5mm TRRS jack, a USB micro-B port
and a TTL serial port via the 9-pin D connector.
The TRRS jack can be configured for either RS232 or RS485. This is selected via the touch screen, the
push-button (see Section 2.3.6) or the commands ENABLERS485 and DISABLERS485. The USB port is
always available serving as a virtual COM port and utilizes the same RS232 command set. The TTL serial
port will not recognize commands that deal with RS485. See section 2.3.7 for TTL connection
information.
5.2.2. Serial Communication Software
Serial Communication Software running on a host computer is required to access the serial port. All
such programs need to be configured to communicate with the instrument; the required parameters
are Baud Rate (Bits per second), the number of data bits (8), Parity (None), Number of Stop Bits (1),
and Flow Control (None).
5.2.3. The Sensor List
Most of the HVG-2020A operational parameters are found in the Sensor List. To read all the
parameters, send the command SL. To read an individual item from the Sensor List (e.g. item #5 Device
Address) send the letter/number combination of the line in the list (e.g. S5 reads the Device Address).
The Sensor List (SL) contains general information about the entire instrument as well as sensor-specific
information.
5.2.4. Command Prompt
The prompt character is a greater than symbol '>' (x3E); when this symbol is received, the HVG-2020A
is ready to accept a new command. Software can use the prompt as an end of response indicator if
this symbol is not used in any text fields (e.g. S54 Comment).
5.2.5. Command Format
The HVG-2020A expects a Carriage Return (0x0D) at the end of each command; Line Feeds (0x0A) are
ignored. Commands can be aborted by sending the Escape character (0x1B) before the Carriage Return
HVG-2020A Instruction Manual
Operation
Calibration
Page 19 of 29
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