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5700A/5720A Series II

Operators Manual

5-48

5-25. Service Request Line (SRQ)

Service Request (SRQ) is an IEEE-488.1 bus control line that the calibrator asserts to

notify the controller that it requires some type of service. Many instruments can be on the

bus, but they all share a single SRQ line. To determine which instrument set SRQ, the

Controller normally does a serial poll of each instrument. The calibrator asserts SRQ

whenever the RQS bit in its Serial Poll Status Byte is 1. This bit informs the controller

that the calibrator was the source of the SRQ.

The calibrator clears SRQ and RQS whenever the controller performs a serial poll of the

calibrator’s IEEE-488 interface, sends *CLS, or whenever the MSS bit is cleared. The

MSS bit is cleared only when ESB, MAV, EAV, and ISCB are 0, or they are disabled by

their associated enable bits in the SRE register being set to 0.

5-26. Service Request Enable Register

The Service Request Enable Register (SRE) enables or masks the bits of the Serial Poll

Status Byte. The SRE is cleared at power up. Refer to “Serial Poll Status Byte” for the bit

functions.

5-27. Loading the SRE

By resetting (to 0) the bits in the SRE, you can mask (disable) associated bits in the serial

poll status byte. Bits set to 1 enable the associated bit in the serial poll status byte. The

following sample program enables the ESB bit.

1Ø ! THIS PROGRAM SETS ESB IN THE SRE

2Ø GOSUB 9Ø! GET AND PRINT OLD SRE

3Ø A% = A% + 32% ! ENABLE ESB (BIT 5)

4Ø PRINT @4,”*SRE “;A% ! “

6Ø GOSUB 9Ø! GET AND PRINT NEW SRE

8Ø END

9Ø PRINT @4, “*SRE?” ! ASK FOR THE SRE CONTENTS

1ØØ INPUT @4, A%! RETRIEVE THE REGISTER CONTENTS

11Ø PRINT “SRE = “;A%

12Ø RETURN

Fluke 5700A Series II User Manual

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