How many IOCP-74 units can be used by one host?
The IOCP-74 does not inherently impose any restrictions. However, a host may limit the actual number of units that can be used for several reasons. Each IOCP-74 requires 8 consecutive locations within the host’s I/O map. These locations can be configured to begin on any 8-byte boundary that does not interfere with other host peripherals. A typical XT/AT style host PC has 1024 I/O locations. Of these, many are occupied by standard, peripherals, thus reducing the actual number of free locations. If your application requires separate interrupts, another limitation may be in the number of interrupts available on the host. As a solution to this problem, the IOCP-74 supports shared interrupts which allows all the IOCP-74s to use the same interrupt channel. The only drawback to shared interrupts is a slightly longer execution time during the interrupt service routine to poll and determine which peripheral actually generated the interrupt.
