User manual

Imagestore HDTV User Manual Installation
Miranda Technologies Ltd Page 205
Connection of General Purpose Interfaces
(GPI’s)
General Purpose Interface ports may be used either to trigger the execution of
a series of internal pre-programmed commands (input) or to monitor the
status of the Imagestore HDTV (output). The process of assigning command
macros to an individual GPI port is described in the Front Panel commands
section of this section.
Input to GPI
Ports GPI 1 through GPI 7 can be allocated as either input or output ports, but
GPI ports 8 and 9 are only available as inputs. Where a GPI port is used as an
input, the command macro may be activated by either connecting or
disconnecting the input line to GPI ground (pin 13) depending whether GPI
'on' or GPI 'off' has been assigned.
Output from GPI
A GPI port may used as an output and its active status, (on), is defined by the
output being internally pulled to ground by a "Darlington" configured
transistor such that an active low will be represented by +0.7V. Lamps or
relays attached to an output GPI may use the GPI +12V supply (pin 8) but the
maximum current drawn from this supply should not exceed 500mA.
Where a GPI output is used to drive a relay coil, reverse voltage protection
diodes should be incorporated in the circuit to protect the Imagestore from
voltage transients.