Page 108
DD8
plus Version 2.20 - September 1998
PARALLEL (GPIO) INTERFACE (Electrical Specifications)
Inputs
The inputs may be driven by passive contact closures as from mechanical switches, or from
open collector NPN transistors, or from active CMOS or TTL circuits. In all cases, the driver must
be able to sink adequate current to operate the optocoupler receivers on the GPIO option board.
All inputs share the same common electrical return path, GPI COMMON. The inputs are electri-
cally isolated from the DD8.
Number of Inputs ............................................................... 12
Input LOW voltage: ............................................................ 0 – > +1V
Input HIGH voltage: ........................................................... +3.3V – > +50V
Max input current (input shorted to GPI COMMON): ......... –5.2mA
Max allowable leakage current for input HIGH: ................. –200
µ
A
Outputs
The outputs are optically isolated solid-state relays. These are capable of driving LED or incan-
descent indicators or mechanical relays or logic circuits. In all cases, power for the indicators
etc. must be supplied externally. When the relays are open, the outputs may optionally be pulled
up to the internally is5V supply or to an external supply depending by linking the relevant
pins on the connector. The outputs can switch DC or AC and share the same common electrical
return path, GPO COMMON. The outputs are electrically isolated from the DD8.
Number of Outputs ............................................................ 16
Max current per output: ..................................................... +/– 350mA
Max ON resistance: ........................................................... 2.5
Ω
Max OFF state voltage: ..................................................... +/– 100V
Max OFF state leakage current: ........................................ 1
µ
A
Additionally, one of the GPO also controls a relay on the option board that can be used to switch
the operating mode of external equipment.
Relay contact rating: .......................................................... 0.5A/125V
APPENDIX - 3
