Programming Microcontroller AT89C51  

 Microcontroller has a function as microprocessor. The different is simplicity of microcontroller that can stand alone with out any component such ADC and external memory. Microcontroller is a kind of integrated circuit that be packed as common IC. The main different is the ability to run the instruction code that is loaded at it's memory. On the other hand, microcontroller is completed with Arithmetic Logic Unit that can run arithmetic operations. With out a program that was loaded in it's memory, microcontroller can do nothing. Microcontroller AT89C51Microcontroller AT89C51 is a product of Atmel Corp, that belong to MCS51 microcontroller family. This microcontroller has a same architecture with  microcontroller 8031, product of Intel Corp. The specification of microcontroller AT89C51 are stated below: - 8 bit data line- 4K Byte of flash memory - Maximum clock frequency is 24MHz- 128 Byte internal  Memory   - Four I/O port - Dual  16 bit timer/counter  Registers of AT89C51Microcontroller AT89C51 has some registers, registers that explain in this tutorial are:- Accumulator- R0 - R7 Example of Simple Program Here are two simple listing program in assembly language, The used assembler is asm51.exe  

   

 Figure 1. At89c51 Application Circuit for running led and seven segment display.

   

- Running Led  

 Figure 2. A photograph of Running Led Circuit.

 $mod51       org 00h      jmp mulai ;program dimulai di sinimulai:       mov r1, #05hloop:        dec r1      mov a, #01h      mov p1, a

      call tundakiri:

rl a      mov p1, a      call tunda      cjne a, #80h, kirikanan:      rr a      mov p1, a      call tunda      cjne a, #01h, kanan      cjne r1, #00h, loop      ljmp mulai ;tunda:       mov r4, #02hulang:       dec r4      mov r3, #0ffhtunda1:      dec r3      mov r2, #0ffhtunda2:      

dec r2      cjne r2, #00h, tunda2      cjne r3, #00h, tunda1      cjne r4, #00h, ulang      retend

 The registers that are used above are r1 to r4, and accumulator too. The port that is used to light on eight LEDs is P1.   - Displaying a Number Using Seven Segment Display  

 Figure 3. A Photograph of Seven Segment Displaying Circuit.

 $mod51      org 00h      jmp mulai      mulai:          mov r6, #00h      mov a, #00h

 ulang:                mov r6, p2      mov p1, r6      lcall tampil1      mov p2, #01000000b      lcall tunda      lcall tampil2      mov p2, #10000000b      lcall tunda      jmp ulang tampil1:mov a, #00h      clr c      mov b, #10      mov a, r6       div ab      cjne a, #00h, ke_1      ljmp nol1ke_1:          cjne a, #01h, ke_2      ljmp sijike_2:          cjne a, #02h, ke_3      ljmp loro  ke_3:          cjne a, #03h, ke_4      ljmp telu  ke_4:          cjne a, #04h, ke_5      ljmp papatke_5:          cjne a, #05h, ke_6      ljmp limake_6:          cjne a, #06h, ke_7      ljmp enemke_7:          cjne a, #07h, ke_8      ljmp pituke_8:          cjne a, #08h, ke_9      ljmp woluke_9:          cjne a, #09h, keluar      ljmp sangakeluar: ret tampil2:mov a, #00h      clr c      mov a, b      cjne a, #00h, ke_12      ljmp nolke_12: cjne a, #01h, ke_22      ljmp sijike_22:        cjne a, #02h, ke_32      ljmp loro  ke_32:        cjne a, #03h, ke_42      acall telu 

ke_42:        cjne a, #04h, ke_52      ljmp papatke_52:        cjne a, #05h, ke_62      ljmp limake_62:        cjne a, #06h, ke_72      ljmp enemke_72:        cjne a, #07h, ke_82      ljmp pituke_82:        cjne a, #08h, ke_92      ljmp woluke_92:        cjne a, #09h, keluar2      ljmp sangakeluar2:ret                       ;      a                        ;    f      b                       ;      g                         ;    e      c                       ;      d                                            ;0gfedcbanol1:           mov p0, #00h      retnol: mov p0, #00111111b      retsiji: mov p0, #00000110b      retloro:           mov p0, #01011011b      rettelu:            mov p0, #01001111b      retpapat:         mov p0, #01100110b      retlima:           mov p0, #01101101b      retenem:         mov p0, #01111101b      retpitu:            mov p0, #00000111b      retwolu:          mov p0, #01111111b      retsanga:         mov p0, #01101111b      ret tunda:  mov r5, #255kurang: dec r5      cjne r5, #00h, kurang      retend

 The listing program above, has a function to display two binary datum that saved in r6. The used display are two seven segment common cathode LED. Datum at a segment to g are attached from P0.0 -P0.6. For sweeping digit once and second we use P2.7 and p2.8