Description: This system senses the speed at which the fan is rotating and adjusts the speed, based on the user input. The user can select three different speeds of the fan. The current speed should be sensed and the control mechanism should gradually increase the speed to the desired speed.
User Interface:
- Fan starts when user presses ‘Start’ button.
- User can then set the required speed by using a keypad interface. This speed value should be displayed on the display.
- After setting speed initially, user should be able to change the fan speed setting by an up and down switch. Each press on this arrow button increases/ decreases the speed by 1 unit. Min speed value is 1, whereas maximum speed value is 5 Units. Pressing ‘UP’ button after reaching to value.
- should not change the display value or setting of fan speed. Same is true for lower bound.
- Fan can be stopped by pressing ‘Stop’ button.
- User can also set the mode of fan as ‘Auto’ mode besides a ‘Regular mode’ setting. In Auto mode, user should be able to enter the value of time in terms of hours after which the Fan has to be switched off automatically. (For example, if value entered is 2, then the Fan should switch off after 2 hours from the time this setting is applied
- 8086 Micro-Processor = 1
- 74LS373 Octal Latches = 3
- 74LS138 3:8 Decoder = 1
- 8255A Programmable Peripheral Interfacing Device = 1
- 7SEG-COM-CAT-BLUE Display = 1
- DAC_8 Digital to Analog Converter = 1
- DC Fan = 1
- Push Button Switches = 16
- 74LS245 Bi-Directional Buffer = 2
- 2732 SROM Chips (2KB each) = 2
- 6116 RAM Chips (2KB each) = 2
- OR Gates = 6
- NOT Gates = 3
- SPDT Switch = 1
- Ground Terminal = as required
| Item | Address | Details |
|---|---|---|
| RAM (Memory) | 02000H – 02FFFFH | 2 * 2 KB Chips |
| ROM (Memory) | 00000H – 1FFFFH | 2 * 2 KB Chips |
| Port A (8255A) | 00H | Output (DC Fan) |
| Port B (8255A) | 02H | Output (7 Segment Display) |
| Port C (8255A) | 04H | Input/Output (Keypad) |
| Control Register | 06H | For loading the Control Word |
- CLK pin of the micro-processor is connected to a reliable clock generator to produce waveform of suitable frequency.
- User can start the fan only by pressing the start button. No other key will function until the fan has been started.
- The fan starts at speed 1 on press of the start button.
- Pressing the start button after the fan has started results in no change of the system state.
- User can then set the speed of the fan by pressing any of the push buttons numbered from 1 to 5.
- Pressing button number 0 essentially serves the same purpose as that of the stop button.
- Auto mode runs only at one speed. (Speed 3)
- Hours in the Auto Mode have been scaled down to Seconds for the sake of simplicity of demonstration.
- Display doesn’t change when working in the auto mode.
- Auto mode allows users to enter numbers from 0 to 10.
.model tiny
.data
table_kbrd dw 0eeh, 0edh, 0ebh, 0e7h, 0deh, 0ddh, 0dbh, 0d7h, 0beh, 0bdh, 0bbh, 0b7h, 7eh, 7dh, 7bh, 77h
table_dis db 3fh, 06h, 5bh, 4fh, 66h, 6dh;, 007dh, 0027h, 007fh, 006fh, 0077h, 007ch, 0039h, 005eh, 0079h, 0071h
speed dw 00h
started dw 00h
auto_speed dw 03h
time dw 00h
auto_flag dw 00h
.code
.startup
porta equ 00h ;setting the 8253a ports
portb equ 02h
portc equ 04h
creg equ 06h
;initializing the ports of 8253a
mov al, 88h
out creg, al
x0: mov al, 00h
out portc, al
x1: in al, portc
and al, 0f0h
cmp al, 0f0h ;check for key release
jnz x1
call delay_20ms ;debounce
mov al, 00h
out portc, al
x2: in al, portc
and al, 0f0h
cmp al, 0f0h
jz x2
call delay_20ms ;debounce
;checking the validity of key press
mov al, 00h
out portc, al
in al, portc
and al, 0f0h
cmp al, 0f0h
jz x2
;check for key press column 1
mov al, 0eh
mov bl, al
out portc, al
in al, portc
and al, 0f0h
cmp al, 0f0h
jnz x3
;check for key press column 2
mov al, 0dh
mov bl, al
out portc, al
in al, portc
and al, 0f0h
cmp al, 0f0h
jnz x3
;check for key press column 3
mov al, 0bh
mov bl, al
out portc, al
in al, portc
and al, 0f0h
cmp al, 0f0h
jnz x3
;check for key press column 4
mov al, 07h
mov bl, al
out portc, al
in al, portc
and al, 0f0h
cmp al, 0f0h
jz x2
;decode key
x3: or al, bl
mov cx, 0fh
mov di, 00h
lea di, ds:table_kbrd
x4: cmp al, [di]
jz x5
inc di
loop x4
;checks if motor is started
x5: cmp started, 01h
jz auto
cmp al, 0b7h ;button encoding for start
jz start
jmp x0
start: call start_fan
jmp x0
auto: cmp al, 0b7h
jz x0
cmp auto_flag, 01h
jz time_set
cmp al, 77h
jnz speed_check
mov auto_flag, 01h
jmp x0
time_set: cmp al, 0eeh; checks which speed
call stop
jmp x0
cmp al, 0edh
jz set_time_1
cmp al, 0ebh
jz set_time_2
cmp al, 0e7h
jz set_time_3
cmp al, 0deh
jz set_time_4
cmp al, 0ddh
jz set_time_5
cmp al, 0dbh
jz set_time_6
cmp al, 0d7h
jz set_time_7
cmp al, 0beh
jz set_time_8
cmp al, 0bdh
jz set_time_9
cmp al, 0bbh
jz set_time_10
jmp x0
set_time_1: mov time, 01h
call set_time
call stop
jmp x0
set_time_2: mov time, 02h
call set_time
call stop
jmp x0
set_time_3: mov time, 03h
call set_time
call stop
jmp x0
set_time_4: mov time, 04h
call set_time
call stop
jmp x0
set_time_5: mov time, 05h
call set_time
call stop
jmp x0
set_time_6: mov time, 06h
call set_time
call stop
jmp x0
set_time_7: mov time, 07h
call set_time
call stop
jmp x0
set_time_8: mov time, 08h
call set_time
call stop
jmp x0
set_time_9: mov time, 09h
call set_time
call stop
jmp x0
set_time_10: mov time, 0ah
call set_time
call stop
jmp x0
;checks which speed to set and sets it
speed_check: lea bx, DS:table_dis
cmp al, 0eeh
jz set_speed_0
cmp al, 0edh
jz set_speed_1
cmp al, 0ebh
jz set_speed_2
cmp al, 0e7h
jz set_speed_3
cmp al, 0deh
jz set_speed_4
cmp al, 0ddh
jz set_speed_5
jmp increase
set_speed_0: mov speed, 00h
call stop
mov al, 3fh
not al
out portb, al
jmp x0
set_speed_1: mov speed, 01h
call set_speed
;mov al, 06h
mov al, [bx + 01h]
not al
out portb, al
jmp x0
set_speed_2: mov speed, 02h
call set_speed
;mov al, 5bh
mov al, byteptr[bx + 02h]
not al
out portb, al
jmp x0
set_speed_3: mov speed, 03h
call set_speed
;mov al, 4fh
mov al, byteptr[bx + 03h]
not al
out portb, al
jmp x0
set_speed_4: mov speed, 04h
call set_speed
;mov al, 66h
mov al, byteptr[bx + 04h]
not al
out portb, al
jmp x0
set_speed_5: mov speed, 05h
call set_speed
;mov al, 6dh
mov al, byteptr[bx + 05h]
not al
out portb, al
jmp x0
increase: lea bx, DS:table_dis
cmp al, 7dh
jnz decrease
call incr
call set_speed
jmp x0
decrease: cmp al, 7bh
jnz stop_fan
call decr
call set_speed
jmp x0
stop_fan: cmp al, 7eh
jnz x0
call stop
mov al, 3fh
not al
out portb, al
jmp x0
.exit
;Delay of 20ms
delay_20ms proc near
mov cx, 2220
x9: loop x9
ret
delay_20ms endp
;starts the fan on speed 1 on press of start button
start_fan proc near
mov speed, 01h
mov al, 33h
out porta, al
mov started, 01h
ret
start_fan endp
;stops the fan on press of stop button
stop proc near
mov speed, 00h
mov al, 00h
out porta, al
mov started, 00h
mov auto_flag, 00h
ret
stop endp
;sets the required speed
set_speed proc near
mov cx, speed
mov al, 00h
x: add al, 33h
loop x
out porta, al
ret
set_speed endp
set_time proc near
mov cx, auto_speed
mov al, 00h
x8: add al, 33h
loop x8
out porta, al
mov bx, time
loop3: mov dx, 50
loop2: mov cx, 2220
loop1: nop
dec cx
jnz loop1
dec dx
jnz loop2
dec bx
jnz loop3
ret
set_time endp
incr proc near
cmp speed, 05h
jge x6
inc speed
mov cx, speed
add bx, cx
mov al, [bx]
not al
out portb, al
x6: ret
incr endp
decr proc near
cmp speed, 00h
jbe x7
dec speed
mov cx, speed
add bx, cx
mov al, [bx]
not al
out portb, al
x7: ret
decr endp
end- Clock generator is not used to supply the clock input to 8086.
- 8253/54 Timer shall be used to create delays in hours while constructing the actual system.
- The
FCS.dsnfile has to be opened in Proteus 7 professional (ISIS 7) - Compile the assembly code in DOSBOX using
ml main.asm. - The compilation will result in a new machine level code with the name
main.com - Double click on the 8086 processor in the design, browse from the code text box to the
main.comand select it. - Run the simulation using the play button provided in ISIS 7.