PCI-DIO48(S)(S) Manual
Page 6-6
Manual 00650-529-1
Change-of-State Interrupts
At Power-up or Reset, a latch disables all IRQ sources on the card. In order to properly
disable/enable interrupts, you must program the Change-Of-State Interrupt Enable Register first.
To program this Change-of-State-Interrupt-Enable Register, write to it at Base B. Data
bits D0 through D5 control ports A, B, and C of the 8255 PPIs as shown in Table 4. Any access
of Base+B will enable the non-COS IRQ associated with
port C bit 3.
Bit
Port Controlled
D0
Group 0, Port A
D1
Group 0, Port B
D2
Group 0, Port C
D3
Group 1, Port A
D4
Group 1, Port B
D5
Group 1, Port C
Table 6-3:
Change-of-state-interrupt-enable Register
Writing a "one" disables the port; writing a "zero" enables it. When IRQs occur the interrupt state
is latched. To clear the latch, write anything to Base F.
