©annax1 PC-technology Keyboard Graphics Interface cards

©annax2 Keyboard Scan matrix fig p SDU - serial data unitfig. p Keyboard interrupt - IRQ1 Scan code ASCII code

©annax3 Keyboard Accessing the keyboard –BIOS memory area called keyboard buffer addresses from 40:17 to 40:1d, 40:80, 40:82, 40:96 to 40:97 - pointers and status bytes addresses 40:1e to 40:3d (32 bytes) - data area fig 34.4 p –Access via interrupts BIOS INT 16H DOS INT 21H –Access directly via ports port 60H, port 64H

©annax4 Graphics Fig p.1045 –Character ROM –Character generator –Attributefig –Signal generator –Video RAMfig –Palettesfig

©annax5 Graphics BIOS data area 40:10video adapter BIOS data area 40:49 to 66 cursor positions, active page, control registers etc. Adress area in RAM: –Text modeB800:0000 –Graphics modeA000:0000 –low byte = character, high byte = attribute

©annax6 Peripherals, Interface cards IRQ(page 394) I/O-address area DMA-channel

7 Peripherals, Interface cards

©annax8 Peripherals, Interface cards Example: I/O-address area for COM ports