ASEA BROWN BOVERI 802267-251V输入模块
I/O端口映射基于奔腾III处理器的SBC包括特殊的输入/输出指令，用于访问驻留在I/O寻址空间（与内存寻址空间分离且不同）中的I/O外围设备。I/O地址空间中的位置称为端口。当CPU解码并执行一条I/O指令时，它在A00至A15线上产生一个16位I/O地址，并识别处理器的M/I/O控制线的I/O周期。因此，CPU包括一个独立的64Kbyte I/O地址空间，可作为字节、字或长字访问。标准PC/AT硬件电路仅为外围设备保留1024字节的I/O寻址空间，从I/O$000到$3FF。所有标准的PC I/O外围设备，如串行和并行端口、硬盘和软盘驱动器控制器、视频系统、实时时钟、系统计时器和中断控制器，都位于该I/O空间区域。BIOS正确初始化和配置所有这些寄存器；通常不需要直接调整这些I/O端口。I/O地址映射中汇总了分配的和用户可用的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
