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FM-531HD / May 2013
A P P E N D I C E S
The FM-531HD is equipped with a GPI (General Purpose Input) control interface –
an eight input optoisolated interface for selecting presets in the first eight memory slots.
The GPI interface provides eight separate General Purpose Inputs which share a com-
mon DC return. The interface connector is a female DB-9 connector with the following
pin assignments. Note that all pins are isolated from the FM-531HD internal circuitry!
FM-531HD GPI Interface
The GPI input circuits are optoisolated by devices having exceptional input/output
isolation. These inputs are designed to work very well in high RF environments and should
not cause ground loop issues when connected to external equipment.
Each of the GPI inputs is current limited by a 475 ohm internal resistance. The LED
device inside the optoisolators is rated at a maximum forward current of 50mA and a
normal operating current of 5mA.
Before connecting external circuitry to the GPI inputs,
first ascertain whether it will be necessary to utilize
additional outboard series resistance in your application!
Use the following table to determine if an external resistance is required and if so,
what value it should be. Note that a one-half watt resistor is sufficient. The resistance
values in the table below have been calculated to result in approximately 5.0 milliamps
forward current through the optoisolator’s internal LED.
GPI Input Number DB-9 Connector Pin Number
One
Pin 6
Two
Pin 2
Three
Pin 7
Four
Pin 3
Five
Pin 8
Six
Pin 4
Seven
Pin 9
Eight
Pin 5
Common Return
Pin 1
Summary of Contents for FM-531 HD
Page 2: ...Technical Manual Wheatstone Corporation May 2013 FM HD Digital Audio Processor FM 531hd...
Page 122: ...page A 2 FM 531HD May 2013 A P P E N D I C E S Appendix A General Specifications A 3 Contents...
Page 128: ...page A 8 FM 531HD May 2013 A P P E N D I C E S Appendix B FM 531HD GPI Interface A 9 Contents...
