SRS Labs Lock-In Amplifier manual SR530 with the RS232 Interface, SR530 with the Gpib Interface

6)Answers are coming back from the SR530 too slowly due to the W6 default setting for the character interval time. Use the W command to speed up the transmission from the SR530. This can cause problems for the GPIB interface if the echo mode is on (switch 6 of SW1).

The SR530 with the RS232

Interface

The RS232 is a popular serial interface standard for bit serial communication. Despite the existence of the standard there are many permutations of control lines, baud rates, and data formats. If you do not have a lot of experience interfacing RS232 equipment you should read Appendix B for a description of the RS232 and interfacing tips.

Data Communications Equipment (DCE)

The SR530 is configured as DCE so that it may be connected directly to a terminal. If the SR530 is to be interfaced with another DCE device, a special cable (sometimes referred to as a 'modem' cable) is required. To use the RS232 interface you must set the switches in SW2 to match your computer's baud rate, parity, and number of stop bits. Refer to Page 7 for details.

Wait Command

The SR530 normally waits until the RS232 'Clear to Send' control line (CTS) is asserted before sending characters. However, some computers do not set and reset the CTS line, possibly causing the SR530 to send data when the computer is not ready to read it. The SR530 may be 'slowed down' using the W command. Sending 'Wn' causes the unit to wait nx4 mS before sending each character over the RS232 bus. The command W0 sets the wait interval to zero and results in the fastest transmission. The wait interval is set to 6 (24 mS)on power-up.

Termination Sequences

The default RS232 termination characters are sufficient to interface with most computers, however, it will occasionally be necessary to send special terminating sequences to fit the requirements of some computers. This can be done with the J command. The format for the

26

command is:

J {n1,n2,n3,n4}

where n1, n2, n3, and n4 are decimal values between 0 and 255 corresponding to the ASCII codes of the desired termination characters. For instance, if the desired termination sequence is an asterisk, (ASCII 42), two carriage returns, (ASCII 13), and a line-feed, (ASCII 10), the appropriate command is:

J 42,13,13,10

If a G command is sent requiring an answer of 24 (sensitivity = 500 mV), the SR530 would respond with the string

24*<cr><cr><lf>

Up to four terminating characters may be specified by the J command. If no arguments are sent with the J command, the terminating sequence returns to the default (echo on: <cr><lf>; echo off: <cr>).

The J command does not affect the terminating character (<cr>) required at the end of commands received by the SR530. It also does not affect the terminating sequence sent with data over the GPIB interface.

The SR530 with the GPIB

Interface

For a brief introduction to the GPIB standard, please read Appendix C at the back of this manual. Before using the GPIB interface you must set the switches in SW1 per the instructions on page 7.

GPIB Capabilities

The GPIB capabilities of the SR530 consistent with IEEE standard 488 (1978) are shown in the table below. Also shown are the responses of the SR530 to some standard commands.

Code	Function
SH1	Source handshake capability
AH1	Acceptor handshake capability
T5	Basic Talker, Serial Poll, Unaddressed to
	talk if addressed to listen
L4	Basic Listener, Unaddressed to listen if
	addressed to talk
SR1	Service request capability
PP0	No parallel poll capability