prog47a.asm

主要是8051源代码

;  PROG47 - Working through the Electronic Breakout Box  
;
;  Simple Test of the LCD.  
;
;  This Application waits for 30 msecs and then puts "Hello" onto the LCD's 
;   Screen.   
;
;  Myke Predko
;  98.06.17
;
;  Hardware Notes:
;  DS87C520 is used as the Microcontroller
;   - Oscillator Speed is 11.052 MHz
;  P2.4-7 are the LCD Data Bits (NOTE: Bits Are Reversed)
;  P0.3 is Pulled up with a 4.7L K resistor and used for the LCD "RS" Bit
;  P0.4 is Pulled up with a 4.7K Resistor and used for the LCD "E" Bit

;  Constant Declarations
define RS=P0.3                  ;  Define the LCD "RS" Bit
define EStrobe=P0.4             ;  Define the LCD "E" Bit

;  Variable Declarations


;  Macros


;  Mainline
 org 0                          ;  Execution Starts Here
MainLine:                       ;  Mainline of the Program

  clr     EStrobe               ;  Make Sure the "E" Line is Low

  acall   Dlay5                 ;  Wait 30 msecs for the LCD to Power Up
  acall   Dlay5
  acall   Dlay5
  acall   Dlay5
  acall   Dlay5
  acall   Dlay5

  clr     RS                    ;  Sending Instructions

  mov     P2,#0C0h              ;  Output the Reset Command
  setb    EStrobe               ;  Try this instead of "E"?
  clr     EStrobe

  acall   Dlay5

  setb    EStrobe               ;  Send the Reset Again
  clr     EStrobe

  acall   Dlay200               ;  Wait 200 msecs

  setb    EStrobe               ;  Send Reset for the Last Time
  clr     EStrobe

  acall   Dlay200

  mov     P2,#040h              ;  Now, Put the LCD in 4 Bit Mode
  setb    EStrobe
  clr     EStrobe

  acall   Dlay200

  mov     A,#028h               ;  Set the Number of Display Lines to 2
  acall   CharSend              ;   and a 5x7 Font

  mov     A,#008h               ;  Turn the Display Off
  acall   CharSend

  mov     A,#001h               ;  Clear the Display RAM
  acall   CharSend

  mov     A,#006h               ;  Enable Cursor Increment
  acall   CharSend

  mov     A,#00Eh               ;  Turn on the Display
  acall   CharSend


  mov     A,#'A'                ;  Put an "A" on the LCD
  setb    RS
  acall   CharSend
  
Loop:                           ;  Loop Here forever
  ajmp    Loop


;  Subroutines
CharSend:                       ;  Send the Character in the Accumulator

  mov     R7,#8                 ;  Have to Reverse the Bits
CSLoop:                         ;  Loop Here Until R6 Has the Value
  rrc a                         ;  Shift the LSB into the Carry Flag
  xch     A,R6                  
  rlc a                         ;  Shift in the New MSB
  xch     A,R6
  djnz    R7,CSLoop             ;  Loop Around

  xch     A,R6                  ;  Save R6 for Tests

  swap a                        ;  Make Low Byte high Byte...
  mov     P2,A                  ;  Output the High Nybble First
  setb    EStrobe
  clr     EStrobe

  swap A                        ;  Now, Output the Low Nybble
  mov     P2,A
  setb    EStrobe
  clr     EStrobe

  acall   Dlay200

  jb      RS,CharSendEnd        ;  If Outputting a Character, Not a Long Instruction

  anl     A,#03Fh               ;  Are we Executing a Long Instruction?
  jnz     CharSendEnd

  acall   Dlay5                 ;  Yes, Delay 5 msec

CharSendEnd:

  ret


Dlay200:                        ;  Use R7 to Delay 200 usecs

  mov     R7,#192
Dlay200Loop:
  djnz    R7,Dlay200Loop        ;  3 Cycles

  ret


Dlay5:                          ;  Use R6 and R7 to Delay 5 msecs

  mov     R6,#0
  mov     R7,#19
Dlay5Loop:
  djnz    R6,Dlay5Loop          ;  3 Cycles
  djnz    R7,Dlay5Loop          ;  3x256 + 3 = 771 Cycles

  ret