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本帖最后由 lcytms 于 2017-3-8 15:34 编辑
Building a System 建立一个系统
To build a usable system you obviously need more than just the processor. 建立一个可用的系统,你需要的不仅仅是处理器。
For a minimum embedded system you would need: 一个最小的嵌入式系统需要:
•An Interrupt Controller. 中断控制器。
Interrupts are an essential part of any system. 中断是任何系统的一个重要组成部分。
The 8088 is normally paired with an 8259A Programmable Interrupt Controller. 8088通常使用一对8259A可编程中断控制器。
Although this device is as old as the 8088 due to legacy issues you will still find it on any modern PC.
虽然这个器件和8088一样古老,但由于继承的原因,你还是能在当今所有的PC机上找到它。
Note that you can not simply connect an device IRQ to the 8088 INTR input without additional glue logic.
注意:你不能简单地连接一个器件的IRQ到8088 INTR输入端,而不使用额外的胶合逻辑。
The reason for this is that an 8088 expects an interrupt vector to be pushed onto the databus during the second Interrupt ACKnowledge cycle.
这是因为8088在第二个中断应答周期中,正常会收到一个被推到数据总线上的中断向量。
•A Timer unit. 一个定时器单元。
Any embedded application even the simplest one needs timers to generate periodic interrupts (e.g. OS task switching, time keeping functions, DRAM refresh etc).
所有的嵌入式应用,即使是最简单的应用,也需要定时器来产生周期性中断(例如操作系统任务开关、计时功能、DRAM刷新等)。
The obvious choice is an 8254/8253 Programmable Timer. 显而易见的选择就是一个8254/8253可编程定时器。
• Parallel I/O Port. 并行I/O口。
For any Parallel I/O operations an 8255 Programmable Peripheral Interface (PPI) can be used.
8255可编程外围接口(PPI)可用于所有的并行I/O操作。
This is a versatile device that can be configure in simple I/O, strobed I/O or fully bi-directional I/O.
这是一个多功能的器件,它可以配置成简单I/O、选通I/O或全双工I/O。
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