More than two decades ago, we developed a device that transmits and receives data using a television signal. Now everyone is spoiled by gigahertz and gigabytes, and then, having a computer like IBM / PC-AT, at such speeds it was possible to work only with the help of the built-in direct memory access controller (DMA), implemented in the form of 8237A-5 microcircuits. This device made it possible to write or read data without involving the central processor.
, , , , . , , , , – , , . , , , ..
, , . 16- 8237-5 «» (.. 128 )
OUT DX,AL
OUT DX,AX
, 8-.
, – ! AX AL – . !
. OUT , INOUT . , AL AX, , ( 83H) AL, , .. 84H – AH, .
? « IBM PC»:
IBM AT:
81h 2
82h 3
83h 1
87h 0
89h 6
8Bh 5
8Ah 7
8Fh
84H!
, , . , , - , 16 .
, , , , , 84. , (DMA) ISA .
. , ! AX AL ? . AL, , , , , . , , ! , .
, . , . , , , (!) , .
But still, this case of luck in my programming practice is out of the ordinary. So don't believe in guardian angels after that. Moreover, specialized, saving from errors in assembly language programs.