For what concern the E497’s internal registers I/O mapping, the following diagram will be useful todescribe how to access to internal of both 82C55 IC. The user, while writes software for E497 board, must take care only for the first 3 bits of addressing. The third bit permits to distinguish between the two 82C55 IC, the first and the secondpermit to access 82C55’s internal registers. 5