●●● 13.2 /0 Hardware ●●●● ●●●●● ●●● ●●●0● o Reading and Writing of registers ●●●0 o Special l/o instructions(Direct O) Transfer a byte or a word to an l/o port address Trigger bus lines to select the proper device Move bits into or out of a device register Memory-mapped l/O Device registers are mapped into the memory address Use the standard data-transfer instructions to read and writer the registers o Direct l0 memory mapped o11 13.2 I/O Hardware ⚫ Reading and Writing of registers ⚫ Special I/O instructions (Direct I/O) ▪ Transfer a byte or a word to an I/O port address ▪ Trigger bus lines to select the proper device ▪ Move bits into or out of a device register ⚫ Memory-mapped I/O ▪ Device registers are mapped into the memory address ▪ Use the standard data-transfer instructions to read and writer the registers ⚫ Direct I/O + memory mapped I/O