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6 - Introduction to Programming
RS-232 Flow Control
The RS-232 interface supports several flow control options that are selected using the front panel
Address key. For each case, the dc source will send a maximum of five characters after holdoff is
asserted by the controller. The dc source is capable of receiving as many as fifteen additional characters
after it asserts holdoff.
XON-XOFF
A software handshake that uses the ASCII control code DC3 (decimal code
19) to assert hold-off, and control code DC1 (decimal code 17) to release
hold-off.
RTS-CTS
The dc source asserts its Request to Send (RTS) line to signal hold-off
when its input buffer is almost full, and it interprets its Clear to Send (CTS)
line as a hold-off signal from the controller.
DTR-DSR
The dc source asserts its Data Terminal Ready (DTR) line to signal hold-
off when its input buffer is almost full, and it interprets its Data Set Ready
(DSR) line as a hold-off signal from the controller.
NONE
There is no flow control.
Flow control options are stored in non-volatile memory.
Introduction to SCPI
SCPI (Standard Commands for Programmable Instruments) is a programming language for controlling
instrument functions over the HP-IB. SCPI is layered on top of the hardware-portion of IEEE 488.2. The
same SCPI commands and parameters control the same functions in different classes of instruments. For
example, you would use the same DISPlay command to control the dc source display and the display of a
SCPI-compatible multimeter.
SCPI References
The following documents will assist you with programming in SCPI:
♦ Standard Commands for Programmable Instruments Volume 1, Syntax and Style
♦ Standard Commands for Programmable Instruments Volume 2, Command References
♦ Standard Commands for Programmable Instruments Volume 3, Data Interchange Format
♦ Standard Commands for Programmable Instruments Volume 4, Instrument Classes
To obtain a copy of the above documents, contact: Fred Bode, Executive Director, SCPI Consortium,
8380 Hercules Drive, Suite P3, Ls Mesa, CA 91942, USA
HP-IB References
The most important HP-IB documents are your controller programming manuals - HP BASIC, HP-IB
Command Library for MS DOS, etc. Refer to these for all non-SCPI commands (for example: Local
Lockout).
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