[求助]谁能给这个程序加上注释-51+8255+液晶显示程序

;PA0~PA7接DB0~DB7，PC7接BUSY，PC0接REQ，CS8255选择CS0(0CFA0H)
 ;8255扩展OCMJ2X8模块测试程序
 ;------------------------------------------------
        PA         EQU  0CFA0H
        PB         EQU  0CFA1H
        PCC        EQU  0CFA2H
        PCTL       EQU  0CFA3H
        STOBE0     EQU  70H        ;PC0复位控制字
        STOBE1     EQU  71H        ;PC0置位控制字

  CSEG AT  0000H
          LJMP  START

      CSEG AT 4100H
;----------------------------------------

START:  MOV DPTR, #PCTL
        MOV A, #88H
        MOVX @DPTR, A              ;置PA口输出,PC口高4位输入,低4位输出
        MOV A, #STOBE0
        MOVX @DPTR, A
        MOV A, #0F4H
   ACALL SUB2
   ACALL DELAY                ;清屏

START1: MOV R0, #01H
  MOV R1, #3CH
HE1:    MOV DPTR, #PCC
        MOVX A, @DPTR
        JB ACC.7, HE1
        ACALL SUB1
         ACALL DELAY1    
     ACALL SUB2
     DJNZ R1, HE1
     ACALL DELAY
        LJMP START
;-------------------------------------------------------
DELAY:  MOV R2, #23H
DEL0:   MOV R4, #06FH
DEL1:   MOV R6, #06FH
DEL2:   DJNZ R6, DEL2
  DJNZ R4, DEL1
  DJNZ R2, DEL0
  RET
;-------------------------------------------------------
SUB2:   MOV DPTR, #PA
        MOVX @DPTR, A
        MOV DPTR, #PCTL
        MOV A, #STOBE1
        MOVX @DPTR, A
        INC R0
;-------------------------------------------------------
HE2:    MOV DPTR, #PCC
        MOVX A, @DPTR
     JNB ACC.7, HE2
     MOV DPTR, #PCTL
        MOV A, #STOBE0
        MOVX @DPTR, A
  RET
;-------------------------------------------------------
DELAY1:  MOV R3,#00    
         MOV R5,#00
DLL:   DJNZ  R3,$
        DJNZ  R5,DLL
        RET
;-----------------------------------------
SUB1:   MOV A, R0    ;显示“临沂师范学院物理系欢迎你”
  MOVC A,@A+PC
  RET
  DB 0F0H,01D,00D,33D,57D
         DB 0F0H,02D,00D,50D,42D
  DB 0F0H,03D,00D,42D,06D
         DB 0F0H,04D,00D,23D,22D
  DB 0F0H,05D,00D,49D,07D
         DB 0F0H,06D,00D,52D,26D
  DB 0F0H,01D,01D,46D,79D
         DB 0F0H,02D,01D,32D,77D
  DB 0F0H,03D,01D,47D,21D
         DB 0F0H,04D,01D,27D,22D
  DB 0F0H,05D,01D,51D,13D
         DB 0F0H,06D,01D,36D,67D

  END