Manual Number: 00431-024-14
Page 2-2
DIO24-P Manual
Setting Base Address
It is easier to think in hexadecimal when determining I/O address. This avoids the decimal-to-hex or
decimal-to-binary conversion required to set the switch. The following example shows how to set
the switches:
1. Desired I/O address: &Hex 300
2. Binary value of address &Hex number
&Hex 300 = 0011 0000 0000 Binary
3. Set switches with ON = 0 and OFF = 1. The lower 2 bits are factory set and are discarded while
the upper two bits are always 0 and are not provided for on the switch. The switch is then set to
(for Hex 300):
The switch positions mirror the bit pattern above with OFF = 1 = DOWN.
Interrupts
The DIO24-P provides for input channels 22 and 23 to generate hardware interrupts. These inter-
rupts can be directed to any of the Interrupt Request Lines (IRQ 2, 3, 4, 5, 6, and 7) available on the
8-bit PC/XT/AT I/O expansion bus.
Pin 1 (Channel 23 is configured as an INTERRUPT INPUT and Pin 3 (Channel 22) is the INTER-
RUPT ENABLE on the DB37 connector. To use the interrupts, simply insert the appropriate IRQ
jumper to select the desired interrupt channel. To determine which input generated the interrupt, read
Port C Upper, bits 6 and 7, to read the current state of the inputs.
Jumper block J2 allows the user to customize the interrupt inputs to use pins 1 and 2 of the I/O
connector. These jumpers are not normally used and interested users are directed to the schematic
for additional details.
You should be aware that an interrupt will be generated if the IRQ jumper is inserted and Port C
Upper is used as an output. This feature could be used to test an interrupt routine without external
connections being required.
