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AM-10HD / Aug 2008
G E N E R A L I N F O R M A T I O N
General Purpose Interface (GPI/GPO)
The AM-10HD is equipped with eight General Purpose Input (GPI) control
input ports on one female DB-9 connector, and four General Purpose Output
(GPO) tally outputs on a second female DB-9 connector. All GPI and GPO
connections are optically-isolated to prevent interference from high-level RF
fields and external ground loops, and also to prevent dangerous voltages from
being introduced into the AM-10HD.
GPI
The GPI interface provides eight separate General Purpose Inputs, sharing a
common return. The connector is a female DB-9 connector with the following
pin assignments. Note that all pins are isolated from AM-10HD internal circuitry!
Pin 1 – GPI COM (-)
Pin 6 – GPI 1 IN (+)
Pin 2 – GPI 2 IN (+)
Pin 7 – GPI 3 IN (+)
Pin 3 – GPI 4 IN (+)
Pin 8 – GPI 5 IN (+)
Pin 4 – GPI 6 IN (+)
Pin 9 – GPI 7 IN (+)
Pin 5 – GPI 8 IN (+)
The GPI input circuits are optoisolated by devices having an input/output
isolation of 1,500VAC. These inputs will work very well in high RF environments
and will not cause ground loop issues when connected to external equipment.
Each of the GPI inputs is current limited by a 475 ohm resistance located
inside the AM-10HD’s GPI control circuitry. The LED device inside the optoiso-
lators is rated at a maximum forward current of 50mA and a normal operating
current of 5mA.
Before connecting external circuitry to the GPI inputs you should first
ascertain whether it will be necessary to utilize additional outboard series
resistance in your application!
The following table will serve as a convenient reference to determine if an
external resistance is required in your application, and if so, what value that
resistance should be. Note that in all applications up to and including 48VDC
a one-half watt resistor power rating is sufficient.
