ECS 50 Lecture Notes - Lecture 26: Bus Mastering, Interrupt Descriptor Table, Interrupt Handler
9 Jul 2016
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I/o write: out: there are separate lines on the bus to distinguish between memory reads and writes (mr and mw) and i/o device reads and writes (i/o r and i/o w, mov will assert either mr or mw. I/o instructions will assert either mr or mw: memory mapped i/o, part of the address space is reserved for i/o devices and the rest is reserved for regular memory, no special instructions are needed for i/o. Polling (aka wait loop i/o: the simplest strategy for getting input from a device is called polling. 0 is the timer, 1 the keyboard, 12 the mouse. Controller: it is a configurable device and the configurations are set by the os. It is even possible to turn interrupts off by using cli: to turn them back on you use sti. Instead of this we can add another piece of hardware called a dma controller and connect the.
