Assalam u Alaikum ! Today I want to share my fourth year's Microcontroller AT89C51 based project of Master Slave Control. Hope it helps you in your studies ! :)
MASTER SLAVE CONTROL
AT89C51
Introduction
There has always been
needs of performing many operations on different locations through a single
controller. Master Slave Control is the technique that provides these features
of performing and controlling various operations in different locations.
As the name suggests,
there is one master controller and one or more slave controllers. AT89C51
supports up to 255 slave controllers that can be utilized in different areas
for different requirements. Master Controller is used to perform certain
operations and instructs the slave controls to perform required operations as
well.
Transmission and
reception between master and slave controls is done serially through the Rx and
Tx pins of the microcontrollers. Multiprocessing ability of the
microcontrollers is thus utilized in this technique. There can also be a shift in
master and slave controllers, one controller can become master or slave at any
instant of time to handle the shifting of controls for required operations.
In our project we have
used master slave control for the delivering the input of keyboard on the LCD
and the LED’s. In our project, keyboard and LCD is attached to the master
controller and the LEDs’ are attached with slave controllers. Each controller
has 8 LEDs’ to show the BCD equivalent of the Number entered from the keyboard.
Block diagram
PROGRAM
MASTER
CODE
lcd_data equ 090h
lcd_e equ P3.5
lcd_rw equ P3.3
lcd_rs equ P3.4
CTWRDARST EQU 01100011B
CNTWRDAOPR EQU 00100011B
CNTRWRBSTART EQU 00011010B
CONFIG EQU 38H
ENTRYMODE EQU 6
OFFCUR EQU 0CH
LINECUR EQU 0EH
BLINKCUR EQU 0DH
COMBNCUR EQU 0FH
HOMECUR EQU 02H
SHLFCUR EQU 10H
SHRTCUR EQU 14H
CLRDSP EQU 01H
OFFDSP EQU 0AH
ONDSP EQU 0EH
SHLFDSP EQU 18H
SHRTDSP EQU 1CH
ORG 0000H
LJMP MAIN
ORG 0003H
LJMP KBRFDISP // KEYBOARD INTERRUPT
MAIN :
LCALL INITRS232 //
INITIALIZE SERIAL
LCALL RESETLCD //RESET LCD
LCALL INITLCD //
INITIALIZE LCD
MOV P2,#OFFH // INPUT FROM KEYBOARD
MOV IE,#100000001B
SETB IT0 // INTERRUPT ENABLE
SJMP $ // REPEAT FOREVER
KBRDISP:
MOV A,P2
ANL A,#0FH
LCALL BCDTOASCII // BCD TO ASCII FOR LCD
LCALL LCALL WRLCDDATA // LCD PRINTING
LCALL PUTCHAR //
SERIAL TRANSMISSION
RETI
PUTCHAR:
JNB TI,$ //
WAIT FOR PREVIOUS DATA TO BE TRANSMITTED
CLR TI
CLR TB8 //PREPARE
FOR TRANSMIT
MOV SBUF,A
SETB TB8
RET
INITRS232:
MOV TMOD,#20H
MOV TH1,#-3
MOV SCON,#11001000B \\
FOR MODE-2 , TB8=1
SETB TR1
RET
RESETLCD:
CLR LCD_RS
CLR LCD_RW
CLR LCD_E
MOV R0,#30H
SETB LCD_E
CLR LCD_E
MOV A,#4
LCALL DELAY
MOV LCD_DATA,#30H
SETB LCD_E
CLR LCD_E
MOV A,#1
LCALL DELAY
MOV LCD_DATA,#30H
SETB LCD_E
CLR LCD_E
MOV A,#1
LCALL DELAY
MOV R0,#CONFIG
LCALL WRLCDCOM
MOV R0,#08H
LCALL WRLCDCOM
MOV R0,#01H
LCALL WRLCDCOM
MOV R0,#ENTRYMODE
LCALL WRLCDCOM
RET
DELAY:
MOV R7,A
AGA:
MOV TH0,#0FCH
MOV TL0,#17H
SETB TR0
WAIT2:
JNB TF0,WAIT2
CLR TF0
CLR TR0
DJNZ R7,AGA
RET
WRLCDCOM:
CLR LCD_E
CLR LCD_RS
CLR LCD_RW
MOV LCD_DATA,R0
LCALL PULSEEWAIT
RET
INITLCD:
CLR LCD_RS
CLR LCD_RW
CLR LCD_E
MOV R0,#38H
LCALL WRLCDCOM
MOV R0,#0EH
LCALL WRLCDCOM
MOV R0,#06H
LCALL WRLCDCOM
MOV R0,#01H
LCALL WRLCDCOM
RET
BCDTOASCII:
CJNE A,#0AH,$+3
JNC BIG
ADD A,#30H
SJMP EXIT
BIG:
ADD A, #37H
EXIT:
MOV R0,A
RET
WRLCDDATA:
CLR LCD_E
SETB LCD_RS
CLR LCD_RW
MOV LCD_DATA,R0
LCALL PULSEEWAIT
RET
PULSEEWAIT:
CLR LCD_E
SETB LCD_E
CLR LCD_E
MOV LCD_DATA,#0FFH
SETB LCD_RW
PUSH ACC
PEW:
INC B
SETB LCD_E
MOV A,LCD_DATA
CLR LCD_E
JB ACC.7,PEW
POP ACC
RET
SLAVE
1 CODING
ORG 0000H
MOV TMOD,#20H //9600 BAUD
MOV TH,#-3
MOV SCON, #0F0H //ENABLE RECEIVER MODE 3 , MULTIPROC
ENABLED
SETB TR1
BACK:
JNB RI,$ // WAIT
FOR CODE
CLR RI
MOV A,SBUF
CJNE A,#0AH,BACK
CLR SM2 // SIMPLE
PROCESSOR
GAIN:
JNB RI,$ // WAIT
FOR DATA
CLR RI
MOV A,SBUF
CJNE A,#ODH,AGAIN
// D IS USED FOR RESET
SETB SM2 // MULTI
PROC ENABLED
SJMP BACK
AGAIN:
MOV P1,A
SJMP GAIN
SLAVE 2 CODING
ORG 0000H
MOV TMOD,#20H //9600 BAUD
MOV TH,#-3
MOV SCON, #0F0H //ENABLE RECEIVER MODE 3 , MULTIPROC ENABLED
SETB TR1
BACK:
JNB RI,$ // WAIT
FOR CODE
CLR RI
MOV A,SBUF
CJNE A,#0BH,BACK
CLR SM2 // SIMPLE
PROCESSOR
GAIN:
JNB RI,$ // WAIT
FOR DATA
CLR RI
MOV A,SBUF
CJNE A,#ODH,AGAIN
// D IS USED FOR RESET
SETB SM2 // MULTI
PROC ENABLED
SJMP BACK
AGAIN:
MOV P1,A
SJMP GAIN
SLAVE
3 CODING
ORG 0000H
MOV TMOD,#20H //9600 BAUD
MOV TH,#-3
MOV SCON, #0F0H //ENABLE RECEIVER MODE 3 , MULTIPROC ENABLED
SETB TR1
BACK:
JNB RI,$ // WAIT FOR CODE
CLR RI
MOV A,SBUF
CJNE A,#0CH,BACK
CLR SM2 // SIMPLE PROCESSOR
GAIN:
JNB RI,$ // WAIT FOR DATA
CLR RI
MOV A,SBUF
CJNE A,#ODH,AGAIN // D IS USED FOR RESET
SETB SM2 // MULTI PROC
ENABLED
SJMP BACK
AGAIN:
MOV P1,A
SJMP GAIN
CONSTRUCTION
In Master Controller:
P1 is connected with
LCD with control inputs from P3.
P2 is connected with
Keyboard through the keyboard decoder MM74C922.
TxD Pin of Master
Controller is connected with RxD pins of all slave controllers.
Each controller is
properly provided crystal frequency, VCC and Ground.
In Slave Controllers:
P1 of each controller
is allotted to 8 LEDs’ to show the BCD code coming from the Master Controller.
WORKING
If
we analyze the program step by step then,
In
main routine:
1- RS232
serial communication is initialized in MODE 2 UART and TB8=1 for addressing in
multiprocessors using suitable value in SCON register also baud rate of 9600 is
set for communication.
2- LCD
is reset and initialized using separate routines.
3- Then
Port 2 which is connected to keyboard is made ready to accept input.
4- Interrupt zero is enabled which is related to
keyboard and on every key press interrupt is activated KBRDISP routine is
activated.
In
KBRDISP routine:
1- Data
from keyboard in port 2 is moved to accumulator.
2- Upper
nibble of data is masked as keyboard consists of 15 keys 0-F.
3- This
masked BCD code is sent to BCDtoASCII routine where it is converted in ASCII to
be shown on LCD by adding suitable values (30H or 37H) in the data in
accumulator.
4- This
ready to display data is sent to WRLCDDATA routine where it is printed on LCD.
5- Then
a Routine called PUTCHAR is called to transmit data to slave controllers.
In
PUTCHAR routine:
1- TI
flag is used to check if the transmitter is busy or ready to send data.
2- Then
by clearing RB8 data is made ready to send, and by using SBUF data is sent and
RB8 is set again for addressing.
So
the process of master controller which is taking data from the keyboard,
writing it to LCD and sending to other slave controllers over TxD is completed.
Now
we move to the Slaves coding where they are ready to accept data.
In
Slaves:
1- First
of all Baud rate of slave controller is set to match with master controller to
achieve proper communication.
2- Then
slave controllers are initialized in mode 3 UART and Multiprocessor is enabled
by moving suitable value in SCON register.
3- Then
Receivers wait for the code to arrive and when it arrives it is checked for the
value of A,B,C for slave 1,2,3 respectively.
4- If
the code of any slave is matched then that slave is activated and Simple
processor is enabled.
5- It
again waits for the inputs from the keyboard and displays on the LEDs’ until D
key is pressed from the keyboard is pressed.
6- D
key of keyboard acts as a reset for the controller and Multiprocessors are
again enabled and the control is transferred to initial position where all the
slave controllers wait for the coming code and all the process is repeated.
Conclusion
This
technique can be employed in the wide distances, where the sent code from the Master
microcontroller can still be seen on slave controllers instead of being distant
from the slave controller. This technique can be employed in industries as well
as other machineries where one needs to handle many machines or equipment using
single remote microcontroller.
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