Input from Keyboard:步骤 USTC When a character is typed: KB Data:its ASCll code is placed in bits [7:0]of KBDR .(bits [15:8]are always zero) - the“ready bit'”(KBSR[15])is set to1 keyboard is disabled(可屏蔽)-any typed characters will be ignored keyboard data 15 87 0 interrupt enable bit KBDR 151413 0 ready bit KBSR interrupt signal ·Vhen KBDR is read: to processor KBSR[15]is set to 0 keyboard is enabled 程序轮询polling?或INTR driven 多任务？Input from Keyboard：步骤 • When a character is typed: – KB Data：its ASCII code is placed in bits [7:0] of KBDR • (bits [15:8] are always zero) – the “ready bit” (KBSR[15]) is set to 1 – keyboard is disabled（可屏蔽） -- any typed characters will be ignored • When KBDR is read: – KBSR[15] is set to 0 – keyboard is enabled • 程序轮询polling或INTR driven • 多任务？