potreadc.asm

包括了各种常用的8051单片机的程序

;  PotReadc - Read the Pot Values Using a 74LS125 
;
;  This Application Reads Resistance Values by Allowing a Capacitor 
;   Wired to a Pot to Charge and then Measure the Time the Cap takes
;   To Discharge.  Instead of using the AT89C2051's I/O Ports, a 74LS125 is 
;   used to Control the State of the I/O Pins Rather than the AT89C2051.
;
;  PotReadc Reads Two Pots
;
;  Myke Predko
;  98.05.11
;
;  Hardware Notes:
;  89C2051 Running at 10 MHz
;  P1.6 is Connected to the Elevator R/C Charge/Discharge Circuit
;  P1.7 is Connected to the Aileron R/C Charge/Discharge Circuit
;  P1.0 is Connected to the R/C Voltage which is the Pulse State
;   Between the Capacitor and Resistor for the Elevator
;  P1.1 is Connected to the R/C Voltage which is the Pulse State
;   Between the Capacitor and Resistor for the Aileron


;  Variable Declarations

 org 0

  mov    TMOD,#%00000010        ;  Put Timer0 in Mode 2
  mov    TH0,#173
  mov    TL0,#173
  setb   TCON.4                 ;  Start the Timer Running

Loop:                           ;  Wait for the Timer to Overflow
  jnb    TCON.5,Loop
  
  nop                           ;  How Long does it take to Get here?  

Mainline:                       ;  Program Mainline

  mov    P1,#%00111111          ;  Allow the Capacitors to Discharge

  mov    R0,#0FFh               ;  Let the Cap Discharge
  mov    R1,#010h               ;  For 10 msecs
Loop1:
  djnz   R0,Loop1
  djnz   R1,Loop1

  mov    P1,#%01111111          ;  Now, Wait for the Elevator Capacitor to Charge

Loop2:                          ;  Loop Until the the Line Becomes High
  jnb    P1.0,Loop2

  mov    P1,#%11111111          ;  Now, Wait for the Aileron Capacitor to Charge

Loop3:                          ;  Loop Until the the Line Becomes High
  jnb    P1.1,Loop3

  ajmp   Mainline