Manual 104-IIRO-8(E)
13
Chapter 5: PROGRAMMING
The board occupies four consecutive addresses in PC I/O space. The base or starting address is selected during
installation and will fall on an eight-byte boundary. The read and write functions are as follows (Model E does not
use Base +2):
I/O Address
Read
Write
Base +0
Base +1
Base +2
Base +3
N/A
Read Isolated Inputs
Enable IRQ
Read digital inputs
Write Relay Output
N/A
Disable IRQ
N/A
ISOLATED DIGITAL INPUTS
Isolated digital input states are read as a single byte from the port at Base A1. Each of the eight bits
within the byte corresponds to a particular digital input. A "1" signifies that the input is energized and a "0"
signifies that the input is de-energized.
Bit
Position
D7 D6 D5 D4 D3 D2 D1 D0
Iso Digital Input
IN7
IN6
IN5
IN4
IN3
IN2
IN1
IN0
The board response to inputs is rated at 10 uSec. Sometimes it is necessary to slow down that response to
accommodate AC inputs or in noisy environments. Hardware installation of JUMPERS to implement filtering is
provided.
The board supports interrupts on change of state of isolated digital inputs. Thus, it is not necessary to
continuously poll inputs (by reading at base a1) to detect any state change. To enable this interrupt
capability, read at base a2. To disable interrupts, write at base a2 or remove the jumper that
selects interrupt level IRQ2 through IRQ7, IRQ10 through IRQ12, IRQ14, or IRQ15. To clear an IRQ, write to
base a1.
DIGITAL INPUTS
Digital input states are read as a single byte from the port at Base A3. Each of the eight bits within the
byte corresponds to a particular digital input. A "1" signifies that the input is high and a "0" signifies that the input
is low.
Bit
Position
D7 D6 D5 D4 D3 D2 D1
D0
Digital Input
DI7
DI6
DI5 DI4 DI3 DI2 DI1
DI0
