Iron - Timer.

Track: By me composed! Xe-xe.. :)        
Author: Macros, 14 July 2K1.             
-----------------------------------------

   +---+-+----+         Таймеры          
  8+D0 |I|CLK1+9                         
  7+D1 |T|CLK2+15                        
  6+D2 | |CLKЗ+18     8253 и 8254        
  5+D3 | +----+                          
  4+D4 | |GAT1+11                        
  3+D5 | |GAT2+14                        
  2+D6 | |GATЗ+16                        
  1+D7 | +----+                          
   +---+ |OUT1+10                        
 21+CS | |OUT2+13                        
   |__ | |OUTЗ+17                        
 23+WR | +----+                          
   |__ | | A0 +19                        
 22+RD | | A1 +20                        
   +---+-+----+                          

  Регистры   счетчиков-таймеров  i8253  и
8254.                                    

The internal counters of the chip have
16 bits, but communication with them
only possible with 8-bit operations. When
this value can only be set
counter low byte (LSB), only
senior (MSB) or both (LSB/MSB), at-
than the younger one is transmitted first, and then
high byte.                            

+====+-+------------------------------+ 
|Port| | Destination | 
+===++ +------------------------------+ 
|040|RW|Counter 0 - system clock (ge-| 
|   |  |irqo neration every 54.936 ms -| 
|   |  |18.206 Hz) | 
|   |  |Mode 3, LSB/MSB, Binary, | 
|   |  |counter=0 (corresponds to the coefficient | 
|   |  | division factor 65536) | 
+---+--+------------------------------+ 
|041|RW|Counter 1 - memory regeneration | 
|   |  |(DRQO for XT, regeneration logic- | 
|   |  |tions for AT) | 
|   |  |Mode 2, LSB, Binary, | 
|   |  |counters=21h | 
+---+--+-------------------------------+ 
|042|RW|Counter 2 - sound generator | 
|   |  |GATE input from bit 0 of port B | 
|   |  |8255 | 
|   |  |Mode 3, LSB/MSB, Binary | 
+---+--+------------------------------+ 
|043|W |Control register | 
|   |  |Bits 7,6 - select counter 0,1,2| 
|   |  |Bits 5,4 - access mode: | 
|   |  |00 - current latchvalues ​​| 
|   |  |01 - LSB - low byte only | 
|   |  |10 - MSB - high byte only | 
|   |  |11 - LSB/MSB - junior first,| 
|   |  |then high bytes | 
|   |  |Bits 3-1 - counter mode: | 
|   |  |000 - counter interrupt | 
|   |  |001 - waiting multivibraotr | 
|   |  |      (one-shot) | 
|   |  |x10 - frequency generator | 
|   |  |x11 - square wave generator | 
|   |  |100 - event counter with resolution | 
|   |  |      sewing | 
|   |  |101 - event counter from restart | 
|   |  |      start | 
|   |  |Bit 0 - 0=Bin (binary count) | 
|   |  |        1=BCD (binary-decimal-| 
|   |  |              account) | 
+===+--+-------------------------------+