51 MCU Simulation Example-EEWORLD

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This is a commonly used program segment - a subroutine - a standard program, which obtains input data or controls output data through port scanning to achieve the purpose of saving bits or bytes - saving hardware resources.

Regarding scanning, we can understand it by starting with the bit and its inversion to realize the running light. The running light-scanning can be realized by shifting. The running light-scanning can be realized by sending the byte data (01H, 02H, 04H, 08H, 10H, 20H, 40H, 80H—anode tube) through the port. The running light-scanning can be realized through the data table (DB 01H, 02H, 04H, 08H, 10H, 20H, 40H, 80H—cathode tube). The running light-scanning can be realized by loop jump. When scanning, pay attention to the input comparison and output check—obtaining input requires comparing data, and sending output requires checking the output.

Scan to get port bytes

Scan output bit movement produces dynamic effects (01, 02, 04, 08, 10, 20, 40, 80), which can be done with byte tables

Scan and output character bytes, and change characters by delay to create a digital carry effect

ORG 0000H

START:

dbuf equ 30h ; set the first address of the storage area

temp equ 40h ; set buffer first address

org 00h

mov 30h,#2 ; store data

mov 31h,#0

mov 32h,#1

mov 33h,#0

mov 34h,#7

mov 35h,#1

mov r0,#dbuf

mov r1,#temp

mov r2,#6 ; six-digit display

mov dptr,#segtab ; segment table first address

dp00: mov a,@r0 ; get the data to be displayed

movc a,@a+dptr ; look up the table to get the segment code

mov @r1,a ;segment code temporarily stored

inc r1

inc r0

djnz r2,dp00

disp0: mov r0,#temp ;display subroutine

mov r1,#6 ; scan 6 times

mov r2,#01h ; start from the first bit

dp01: mov a,@r0

mov p2,a ; segment code output

mov a,r2 ; get bit code

mov p1,a ; bit code output

acall delay ; call delay

mov a,r2

rl a

mov r2,a

inc r0

djnz r1,dp01

sjmp disp0

segtab: db 0C0H,0F9H,0A4H,0B0H,99H,92H ; common anode tube

db 82H,0F8H,80H,90H,88H,88H,83H

delay: mov r4,#29h ;delay subroutine

aa1: mov r5,0ffh

aa: djnz r5,aa

djnz r4,aa1

right

end

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Scanning can also be performed in other program forms, such as loops, incrementing or decrementing judgment programs, etc. Scanning technology can be used for dot matrix displays and liquid crystal display (LCD) displays. These require character encoding, display delay, and scanning ports to make full use of resources (save resources).

Example 1 - About dynamic display - LED flashing

ORG 0000H

START:

MOV A,#0FFH ; Byte transfer

MOV P3,A ; Byte transfer

MOV P1,A

MOV C, 0A0H ；bit transfer

JNB 0A0H, GUAN; if the bit level is low, it is true, then transfer; if the direct address bit is 0, transfer

MOV P1,#00H; P1 port is first assigned #0FFH, then assigned #00H, which will cause flickering

RIGHT

GUAN :

MOV P3,#00H; assign #0FFH to port P3 first, then assign #00H, which will cause flickering. You can also use the inversion instruction

RET ; can produce a flashing effect

END

Other methods (such as delay subroutines) can also achieve dynamic display. [page]

Example 2 - Simulation of a single LED light and a single button

ORG 0000H ; This is a pseudo instruction. The machine does not execute it. It is used for program communication. The starting address of instruction execution is represented by D in decimal, H in hexadecimal, and B in binary. One byte (8-bit machine, 16-bit machine, 32-bit machine, 64-bit machine) is executed at a time. It can also be executed bit by bit, that is, one bit.

ORG 00000000B has the same function as ORG 0000H. Note that 8 bits are one byte. A 16-bit processor needs to be represented by 0000 0000H. For 16 or 32 bits or above, it is more effective to use an operating system (Wince, Linux, etc.), which can utilize a large number of low-level, professional, and standardized control-oriented library functions (such as: API, etc.).

START: ; This is a pseudo instruction, the machine does not execute it. It is just for the sake of the comprehensibility of the assembly language story.

　 MAIN: ; Pseudo instruction, main program, used to distinguish subroutines

　 PC→MOV A, #00H ; transfer the immediate value 00000000B (constant 0D) to the accumulator ACC (special register, which can be used to store calculation results, etc.). To exchange data with other storage addresses through accumulator A. Note that PC is automatically shifted (automatically +1) to the address of the next statement. Using this statement essentially gives PC an initial position.

PC→MOV P1, A ; transfer the number in the accumulator (constant 0D) to port P1 (all 8 bits of port P1 are set to 0, low level, all bits of port P1 are in the off state, and the LED light is in the ready state for system response), and transfer data by byte. Special memory: PC→ indicates the address pointed by the pointer, and it will automatically increase by 1.

PC→MOV C, 0A0H ; Check the status of P2.0 port, and transfer the status of P2.0 port (determined by the key status) to the bit accumulator C. The address of bit accumulator C is the carry flag CY (D7H\PSW.7) of PSW (Program Status Word Register). P2.0 port can be on or off, that is, set to 1 or 0, high level or low level), and data is transferred by byte. Data is exchanged through bit accumulator C and other storage addresses. This statement can also be written as: MOV C, P2.0, compare byte data transfer MOV A, #00H or MOV A, P1.

PC→MOV P1.0, C; equivalent to MOV 90H, C; transfer the value in the bit accumulator C address to the P1.0 port (90H is its direct address), that is, transfer the state of the P2.0 port (determined by the direct address 0A0H state) to the direct address 90H, P1.0 port

PC→MOV P1.1, C ; equivalent to MOV 91H, C

PC→MOV P1.2, C ; equivalent to MOV 92H, C

PC→MOV P1.3, C ; equivalent to MOV 93H, C , etc.

END; pseudo instruction, program end mark

Example 3 - Scanning to achieve digital movement change simulation

Example 4 - Dual-digital tube dual-port digital carry simulation

Example 5 - Dual-port digital display of dual-quadruple digital tube group - Single-port scanning mobile simulation - Dot matrix

Dual quad digital tube set dual port digital display - single port scanning mobile simulation, can be decomposed into

a) Dual-port digital display of dual-quadruple digital tube group - single port no scanning no movement - > digital changes (depending on the digital meter and pointer),

b) Dual-port digital display of dual-quadruple digital tube group - single-port scanning movement - > the number does not change (depending on the number table and pointer),

c) Dual-port digital display of dual-quadruple digital tube group—single-port scanning movement—>digital changes (depending on the digital meter and pointer),

Reference address：51 MCU Simulation Example

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