OPERATION
2-23
Mechanical Description:
The handler interface is part of the Option 01 GPIB/Handler board and is accessed via a 25 pin male
connector on the rear of the SR720/715. A DB25 female connector, metal housing, and plastic sheath have
been provided to simplify construction of a cable to the external handler.
Connector pinouts are as follows:
Pin #
Bin 0: 13
Bin 1: 25
Bin 2: 12
Bin 3: 24
Bin 4: 11
Bin 5: 23
Bin 6: 10
Bin 7: 22
Bin 8: 9
Bin 9: 21
-BUSY: 8
-BDA: 20
-START: 3
Also: +5 supply pins 7 and 19
GND pins 6 and 18
Electrical Description:
The trigger input (-START) line is active low and requires a pulse width of at least 50ns to activate (edge-
triggered). 1N4148 diodes protect against voltages exceeding TTL levels. Outputs are provided by 7406
inverting buffers which have open-collector outputs and therefore need pull-up resistors for proper operation.
NOTE: Maximum High-level output voltage: 30 V
Maximum Low-level output current: 40 mA
Example: When connecting the output to a 5V supply, the pull-up resistor should be no smaller than 5V/40mA
= 125 ohms.
Flyback diodes should be added if the outputs are used to drive relay coils, but such a direct connection is not
recommended. Ideally, opto-isolators should be used on all data lines to prevent noise from the handler from
interfering with measurements.
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