Technical information

Opto IN24 OPTO DIO Reference
contacts, do not necessarily have their own power source. So a
switch by itself connected to the Opto IN24 card will not drive
the input circuitry no matter if it is open or closed. When the
ISO+12 volts is taken from the IN24 card, passed through the
switch and then back to the input port pin a current can flow
when the switch is closed. The current is limited by the 3k3
Ohm resistor on board the IN24 and so no more than 12
Volts/3300 Ohms = 3.6 milli amps is drawn. The power used is
W= VI= 44 milli Watts. Thus if all 24 inputs are driven by the
isolated +12 whetting voltage the total power consumed would
be 1.047 Watts. This is about half the capacity the on board
converter can supply.
Interrupt Selection._________________
The Opto IN24 card can produce interrupts from low to
high transitions on three signal lines, Watch Dog timeout, Port
C2 input bit 0 and Port C2 input bit 3.
The IRQ must be ENABLED in software AND the IRQ
jumper must both be set before any IRQ requests are generated.
Thus IRQs can be enabled under program control to suit the
changing needs of the application. The position of the jumper
MUST match the IRQ level set in the software.
The IRQ enable bits in the watch dog register selects
which Opto IN24 signal generates the interrupt, the IRQ jumper
block selects which PC interrupt line is asserted, and so which
software interrupt service routine is called. Write your IRQ
service routine to patch the appropriate software interrupt.
Watch Dog Selection.___________________
One set of jumpers, at the upper left side of the card, are
used to control the Watch Dog output function, this determines
which signal is used to generate an interrupt or reset signal. The
watch dog enable register is an 8 bit read write register, see
Chapter 1.
Chapter 6 Page 71