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Rs-232 flow control, Rs-232 programming example – Agilent Technologies 6631B User Manual

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Introduction to Programming - 2

11

Baud Rate

The front panel Address key lets you select one of the following baud rates, which is stored in non-volatile
memory:
300

600

1200

2400

4800

9600

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.

RS-232 Programming Example

The following program illustrates how to program the power supply using RS-232 to set the output voltage
and current and to readback the model number and output voltage. The program was written to run on any
controller using Microsoft QBasic.

NOTE:

The power supply must be configured for RS232 and the same baud rate and parity as
the controller.


‘ Program to write and read via RS232.

‘ Configure the power supply for 9600 baud, even parity and RS232

‘ Configure serial port for:”

9600 baud

7 bit data

2 stop bits

Ignore request to send

Ignore carrier detect

Even parity

‘ Needed with Vectra basic, ignored with QBasic

Send line feed

Reserve 1000 character buffer for serial I/O


DECLARE FUNCTION gets$ ()

CLS

‘ Clears screen

LOCATE 1, 1

‘ Position curser at top left

‘ Configure Com Port

OPEN “com1:9600,e,7,2,rs,cd,pe,lf” FOR RANDOM AS #1 LEN = 1000

PRINT #1, “OUTPUT ON”

‘ Turn on output then set voltage and current

PRINT #1, “VOLT 6”

‘ Set voltage to 6 volts

PRINT #1, “CURR .5”

‘ Set current to 0.5 amps

PRINT #1, “*IDN?”

‘ Query the power supply identification string

PRINT gets$

‘ Go to gets$ Function and print data returned

PRINT #1, MEAS”VOLT?”; volt

‘ Query the power supply voltage

Volt = VAL (gets$)

‘ Convert gets$ string to a value

PRINT gets$

‘ Print the value of the voltage

END

‘ End of main program

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