Data Communications Equipment (DCE)

The SR510 is configured as DCE so that it may be connected directly to a terminal. If the SR510 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 SR510 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 SR510 to send data when the computer is not ready to read it. The SR510 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 command is:

J {n1,n2,n3,n4}

where n1, n2, n3, and n4 are decimal values between 0 and 255 corresponding to the decimal 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 SR510 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 SR510. It also does not affect the terminating sequence sent with data over the GPIB interface.

The SR510 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 SR510 consistent with IEEE standard 488 (1978) are shown in the table below. Also shown are the responses of the SR510 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

DC1

Device Clear capability

RL0

REN,LLO, GTL not implemented.

 

'I' command sets Remote-Local.

SR510

Response to GPIB Commands

Mnemonic

Command

Response

DCL

Device Clear

Same as Z command

SDC

Selected

Same as Z command

 

Device Clear

 

SPE

Serial Poll

Send Status Byte,

 

Enable

& clear status byte

Because the SR510 can be controlled by an RS232 interface as well as the GPIB, the remote- local functions are not standard. There is no local with lock out state. When in the local state, remote commands are processed, even without the REN command being issued. This is because

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