ASEA BROWN BOVERI 802267-251V輸入模塊
I/O端口映射基于奔騰III處理器的SBC包括特殊的輸入/輸出指令，用于訪問駐留在I/O尋址空間（與內(nèi)存尋址空間分離且不同）中的I/O外圍設(shè)備。I/O地址空間中的位置稱為端口。當(dāng)CPU解碼并執(zhí)行一條I/O指令時，它在A00至A15線上產(chǎn)生一個16位I/O地址，并識別處理器的M/I/O控制線的I/O周期。因此，CPU包括一個獨(dú)立的64Kbyte I/O地址空間，可作為字節(jié)、字或長字訪問。標(biāo)準(zhǔn)PC/AT硬件電路僅為外圍設(shè)備保留1024字節(jié)的I/O尋址空間，從I/O$000到$3FF。所有標(biāo)準(zhǔn)的PC I/O外圍設(shè)備，如串行和并行端口、硬盤和軟盤驅(qū)動器控制器、視頻系統(tǒng)、實(shí)時時鐘、系統(tǒng)計時器和中斷控制器，都位于該I/O空間區(qū)域。BIOS正確初始化和配置所有這些寄存器；通常不需要直接調(diào)整這些I/O端口。I/O地址映射中匯總了分配的和用戶可用的I/O地址
I/O Port Map The Pentium III processor-based SBC includes special input/output instructions that access I/O peripherals residing in I/O addressing space (separate and distinct from memory addressing space). Locations in I/O address space are referred to as ports. When the CPU decodes and executes an I/O instruction, it produces a 16-bit I/O address on lines A00 to A15 and identifies the I/O cycle to the processor’s M/I/O control line. Thus, the CPU includes an independent 64Kbyte I/O address space, which is accessible as bytes, words, or longwords. Standard PC/AT hardware circuitry reserves only 1,024 bytes of I/O addressing space from I/O $000 to $3FF for peripherals. All standard PC I/O peripherals such as serial and parallel ports, hard and floppy drive controllers, video system, real-time clock, system timers, and interrupt controllers are addressed in this region of I/O space. The BIOS initializes and configures all these registers properly; adjusting these I/O ports directly is not normally necessary. The assigned and user-available I/O addresses are summarized in the I/O Address Map
