Date: 5 June 1991
Re: GPIB (IEEE-488) interface problems.
Affected instruments: SR510 Single Phase Lock-in,
SR530 Dual Phase Lock-in,
SR245 Boxcar Computer Interface
Symptoms: Error indications when used with fast GPIB controllers
Problem:
The GPIB controller which is used in these instruments (Motorola MC68488) will acknowledge
data acceptance about 100 ns prior to actually reading the data. Very fast GPIB controllers can
change the data to the next value during this interval, causing errors.
Solution:
The data acceptance signal, DAC or NDAC must be slowed by about 100 ns. This may be done by
placing a 270 pF capacitor between pin 10 (ground) and pin 17 (DAC) on the GPIB bus driver (Part
Number 75161) which is adjacent to the MC68488 controller.
1290 D Reamwood Avenue, Sunnyvale, CA 94089 Telephone: (408) 744-9040 Fax: (408) 744-9049, Telex: 706891 SRS UD
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