3.1. USB and RS-232 interface
It is recommended to turn off the device with mains switch before connecting/disconnecting the interface cable.
If the device is equipped with both RS-232 and USB interface, only one of them must be connected at the same time.
3.1.1 Programming
The following description applies to both RS-232 and USB interface.
The (virtual) serial interface is set to 9600 Bit/second, 8 Bit/character, no parity, 1 Stop-Bit.
The data transfer is character oriented, and the synchronization in the direction "Computer to high voltage device” (Input
direction) is established by echoes. That means every character received by the device on the RXD line is sent back over the TXD
line to the computer. The transfer direction “HV-PS to computer” (Output direction) is free running, i.e. without echo.
The command transfer uses ASCII characters. Every command line is terminated by
<C R ><L F > ( 0 x 0 D 0 x 0 A o r 1 3 1 0 )
.
A new command may be sent immediately after the last answer was completely received (including <CR><LF>). For commands
that don't return an answer, the simplest thing is to add *OPC? in
(see chapter 12: References) :
Command sent by Computer
Echo and answer sent by HV device
: V O L T 5 0 0 ; : V O L T O N ; *O P C ? <C R ><L F >
: V O L T 5 0 0 ; : V O L T O N ; * O P C ? <C R > <L F >
1 <C R ><L F >
Table 4: Programming serial interface
3.1.2 RS-232 interface
The RS-232 interface is implemented with a female D-SUB-9 connector. Depending on the device, the connector is located at the
front or the back panel.
The electric transfer is performed via the RXD and TXD lines, which are related to floating GND of the interface. The D-SUB 9 pin
assignment is given in the following table.
The cable connection to the computer is direct (1:1, no null-modem-cable). If no 9-pin cable is available, the internal connection
bridges for pin 4, 6, and 8 must be set up externally.
Signal
HV device
Computer
RS-232
D-SUB 9
Internal
D-SUB 9
RXD
2
2
TXD
3
3
GND
5
5
DTR
4
┐
(bridged)
4
DSR
6
┤
(bridged)
6
CTS
8
┘
(bridged)
8
Table 5: D-SUB 9 pin assignment
SCPI protocol common instruction set | Last changed on: 2020-11-10 |
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