T.Y. Diploma : Sem. V [EJ/EN/ET/EX/DE/IS/IC/IE/EV/MU] Micro-controller

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1 T.Y. Diploma : Sem. V [EJ/EN/ET/EX/DE/IS/IC/IE/EV/MU] Microcontroller Time : 3 Hrs.] Prelim Question Paper Solution [Marks : 100 Q.1(a) Attempt any THREE of the following: [12] Q.1(a) (i) Distinguish between Microprocessor and Microcontroller (any four). (A) (Any four points 1 mark each) Micro-processor Micro-controller rolle 1) Micro-processors do not have inbuilt RAM or ROM. Micro-controller roller do have inbuilt RAM or ROM. 2) Memory, I/O ports, timers, Memory, I/O ports, interrupts, interrupts are not integrated inside timers, are integrated inside the the chip. chip. 3) Micro-processors to work as micro- Micro-controllers controllers can be worked as computers requires many additional micro-computers computers without any components to perform its additional components. operation. 4) Program and data are stored in same memory. Separate program and data memory. 5) Booleans operations are not possible directly. Boolean operations are possible directly. 6) e.g. Pentium series, Intel 8086 e.g. 8051, PIC 16F series Q.1(a) (ii) Draw the block diagram of Harvard and Von-Neumann architecture. (A) Harvard architecture CPUdy CPU Data bus Address bus Data bus Address bus Von-Neumann architecture CPU Data bus Address bus Data Memory Program Memory onk ar Program Memory Data Memory 307/379/e:1114/1114/TY/Pre_Pap/Ele/2014/CP/MC_Soln 1

2 : T.Y. Diploma MC Q.1(a) (iii) List any four important features of 8051 microcontroller. (A) Features of 8051 Micro-controller are as follows : 1) It has 8-bit CPU. 2) It has 4kb on-chip program memory. 3) 128 bytes of on-chip data memory. 4) It has 32 bi-directional I/O lines. 5) It has two 16-bit timers/counters. 6) It has 5 vector interrupts. 7) It has full duplex asynchronous receiver transmitter (one serial port) 8) It has on-chip clock oscillators. Q.1(a) (iv) Describe any four addressing modes of 8051 microcontroller with one example each. (A) Types of addressing modes are as follows : (a) Immediate addressing mode : Immediate e addressing mode means the data is provided as a part of instruction (it immediately follows instructions opcode). e.g. MOV A, 99 This instruction directly moves the data 99 to the accumulator. (b) Register addressing mode : It uses registers to hold the data to be manipulated. There are 4 banks of 8 registers. Only one bank is activated at a time which contains R0 to R7 registers. Any one register can be specified as operand. e.g. MOV A, R5 Here, e, content of R5 is copied to the accumulator. (c) Direct addressing mode : This mode is provided to access internal data memory directly including SFR. In this, 8 bit internal data memory address is specified as a part of instruction. It can specify address only from 00H to FFH. e.g. MOV A, 47H This reads the data from internal RAM address 47H and copies it to accumulator. cumu (d) Indirect addressing mode : This is used to hold the actual address which will be used in data movement. R 0, R 1 and DPTR only can be used as data pointers R 0 and R 1 can hold 8 bit while DPTR can hold 16 bit address. It cannot be used for SFRs. e.g. i) MOV 1 R 1 contains the address of internal RAM location, it copies content of memory location pointer by R 0 into A. 2

3 Prelim Question Paper Solution ii) MOV X DPTR It copies the content of external data memory pointed by DPTR into accumulator. Q.1(b) Attempt any ONE of the following : [6] Q.1(b) (i) Describe the power saving operation of 8051 microcontroller. [6] (A) There are 2 types of modes in power saving : (i) Ideal mode (ii) Power down mode (i) Ideal Mode : After setting the ideal bit in PCON register, microcontroller turns into ideal saving mode. In this, content t of all registers, I/O ports remains unchanged serial ports, timers, interrupts continues operating normally. In this system turns of CPU. In order to come out from Ideal mode. Interrupt or Reset signal can be used which will automatically clear ideal bit. C 2 Chrystal C 3 Oscillator pins Osc r PD IDL (ii) Power Down Mode : After setting bit PD in the PCON register, micro- controller turns into power down mode. In this mode, micro-controller turns off its internal oscillator which reduces power consumption which makes micro-controller controller works on 2V power supply and current upto 40 A. In this mode all contains of SFRs and I/O port remains as it is. Q.1(b) (ii) Draw interfacing diagram of 2Kbyte EPROM and 2K byte RAM to 8051 microcontroller. Draw the memory map. (A) For 2 K byte EPROM, 2 Kb = 2 11 A 15 A 14 A 13 A 12 A 11 A 10 A 9 A 8 A 7 A 6 A 5 A 4 A 3 A 2 A 1 A For 2 K byte RAM, 2 Kb = 2 11 Clock generator Interrupt serial port V0V CPU [6] 3

4 : T.Y. Diploma MC A 15 A 14 A 13 A 12 A 11 A 10 A 9 A 8 A 7 A 6 A 5 A 4 A 3 A 2 A 1 A EA WR RD PSEN A 15 A 14 A 13 A 12 A 11 A 8 to A 10 ALE AD 0 to AD 7 74LS 373 Latch Q.2 Attempt any FOUR of the following owing : [16] Q.2(a) Draw the internal architecture re of 8051 microcontroller. (A) Internal Architecture of 8051 microcontroller WR CS 2kb 8 RAM A 8 to A 10 A 0 to A 7 D 0 to D 7 OE +V RD CC +V CC GND A 11 to A 15 WR CS 2kb 8 EEROM A 8 to A 10 A 0 to A 7 OE D 0 to D 7 kar GND nkgnda 4

5 Prelim Question Paper Solution Q.2(b) Explain a Boolean processor of microcontroller 8051 with two examples. (A) The 8051 instruction set is optimized for the one-bit operations so often desired in real-world, real-time control applications. The Boolean processor provides direct support for bit manipulation. ion. This leads to more efficient programs that need to deal with binary input and output conditions inherent in digital-control problems. Bit addressing can be used for test pin monitoring or program control flags. For example, instructions for Boolean function are as given below : (a) ORL P0, #1 ; Set P0.0 (b) XRL P0, #1 ; Toggle P0.0 (c) ANL C, P1.4 ; AND the bit on P1.4 with carry (d) ANL C,!(P1.4) ; AND inverted bit on P1.4 with carry Q.2(c) Describe the function of following pins of 8051 microcontroller (i) PSEN (ii) ALE (iii) EA (iv) RST (A) Functions : (i) PSEN (pin 29) Program strobe enable is the output control signal. It remains low while fetching data from external program memory. During the internal program execution, it remains high. (iii)v (ii) ALE (pin 13) It is address latch enable which is used to demultiplex AD 0 to AD 7 of port 0, it is a positive going pulse generated everytime during external memory access. It latches low order address bus and generates separate set of address lines as shown in diagram. 7y AD 0 -AD ALE ALE G LATCH D 0 D 7 an A0 to A7 (iii) EA (pin 31) When external access pin is enabled, i.e. it is high, it select internal program memory, if it is low, it selects only external program memory. (iv) RST (pin 9) This is reset pin. It provides reset mechanism to establish initial condition if micro-controller hangs. Reseting operation will clear all the content of memory location. 5

6 : T.Y. Diploma MC Q.2(d) Draw the internal RAM memory organization of 8051 microcontroller (A) Internal RAM Memory 7F 30 2F F GPR 16,Bit addressable Registers R 7 R 0 R 7 R 0 R 7 R 0 R 7 Scratch PAD RAM Bit Addressable RAM Register Bank 3 Register Bank 2 Register Bank 1 [stack] 07 Bank 0 00 R 0 RAM Memory : There are 128 bytes of RAM in 8051 assigned address 00 to 7FH. laregister The 128 bytes are divided into 3 different groups as follows : (i) A total of 32 bytes from location 00 to 1F hex are set aside for register banks and the stacks. (ii) A total of 16 bytes from locations 20H to 2FH are set aside for bit addressable read/write memory. (iii) ii) A total of 80 bytes from location 30H to 7FH are used for read and write storage called as scratch pad. ank ar 6

7 Prelim Question Paper Solution Q.2(e) Write an assembly language program for 8051 microcontroller to transfer ten bytes of data from source to destination in internal RAM (Assume suitable memory addresses) (A) Algorithm : Flow Chart : 1. Start Start 2. Initialize memory pointer as source Initialize M.P. as 3. Initialize memory pointer as destination source 4. Initialize counter 5. Move content of 1 st Initialize M.P. as source location to A 6. Move content of A to 1 st destination tion destination location 7. Increment source location MOV content of 1 8. Increment destination location location to A 9. Decrement iteration count if not 0, Move content of A to 1 jump to step 5 destination location 10. Stop Program : ORG 0000H MOV R0, #70H MOV R1, #80H MOV R4, #0AH UP : MOV R0 R1, A INC R0 INC R1 DJNZ R4, UP END Q.3 Attempt any FOUR of following : [16] Q.3(a) Explain the following instruction of 8051 : (i) RLA (ii) MOV (iii) ii) MUL AB (iv) CLRA (A) (i) RLA : Rotate A left (ii) MOU Ua add1 a Ri : Move the content of memory location pointed by R i into add1. (iii) MULAB : multiply A and B (iv) CLRA : Clear A ka Increment source location destination location Decrement iteration count anincrement a loc if count = 0 Yes Stop ank kar r No 7

8 : T.Y. Diploma MC Q.3(b) Describe the following directives with one example. (i) ORG (ii) DB (iii) EQU (iv) END (A) Assembler directives : (i) ORG : The ORG directive is used to indicate the starting address. It can be used only when program counter needs to be changed. It can be decimal or hex. e.g. 2000H; set program counter 2000 (ii) DB (Define byte) : DB directive is used to define 8 bit data. It initialized memory with 8 bit value. It can be decimal, binary or in ASCII formats. e.g. (1) DB 40H ; Hex (2) DB B ; binary (3) DB 16 ; Decimal (4) DB HELLO ; ASCII (iii) EQU (or SET) : These directives assigns numerical value or register name to the specified symbol name. EQU is used to define constant without storing it in memory. Symbol defined EQU should not be redefined whereas SET allows redefinition of symbol. e.g. (1) SET R1 ; use R1 as pointer (2) EQU R1 ; use R1 as a counter (iv) END : This indicates END of program to assembler any text after END is ignored, if END is missing assembler generates error message. Q.3(c) State the function of editor, assembler, linker and compiler. (A) Software development cycle involves the use of following tools : (i) Editor : Editor is used to type the program which produces ASCII file, it can be used to create or edit program. Software code is written in programming language i.e. assembly or C. The file extension is.asm or.src depending of assembly used. (ii) Assembler : It converts the instructions into machine code assembler produces an object file and least file. Extension for object file and least files are.obj and.lst respectively. (iii) Linker : Linker program takes one or more object code files and produces an absolute object file with the extension.abs. (iv) Compiler : It is a software which monitors any flaw (error) in the program written by the programmer and draws the attention of the programmer to all the lines with errors. 8

9 Prelim Question Paper Solution Q.3(d) Write an assembly language program for 8051 microcontroller to add two 8 bit numbers 55H and 67H. Store the result at 20H. (A) Algorithm : Flow-Chart : 1. Initializaiton 2. Get 1st no. in accumulator Start 3. Get 2nd no. in R5 Get 55H in 4. Add both numbers accumulator 5. Store the result in internal memory Get 67H in location 20H R5 6. Stop Program : ORG 0000H MOV A, #55H MOV R5, # 67H ADD A, R5 MOV 20H, A END Add both the numbers Store the result 20Hk in 20H Stop nktop Q.3(e) Discuss the selection factors of microcontroller. (A) Selection factors of microcontroller controller Three criteria in choosing microcontroller are as follows : A) 1) Microcontroller roller must be meet the computing need of the task at hand efficiently and cost. 2) We must whether her an 8 bit, 16 bit or 32 bit micro-controller can best handle the computing needs of the task most effectively. Some other consideration in this category are : i) Speed : What is the highest speed that the micro-controller supports. ii) Packaging : Does it come in 40 pin DIP or QFP (Quad Flat Package) or Some other packaging formats. This is important in terms of space, assembly and prototyping the end product. iii) Power consumption : This is especially critical for battery powered product. iv) The amount of RAM and ROM on chip. v) The number of I/O pins and Timer on chip. vi) Cost per unit. a B) Second criteria in choosing micro-controller is, how easy it is to developed product around it. Key considerations includes the availability of a assembler, debugger, a code efficient C language compiler, emulator, technical support and both inhouse and outside expertise. 9

10 : T.Y. Diploma MC C) The third criteria in choosing the micro-controller is, its ready availability in needed quantity both now and in future currently, of the leading 8 bit micro-controller the 8051 family has the largest number of supplies. In case of 8051, which was diversify originated by Intel. Several companies also producing the These companies includes Intel, Atmel, Philips/Signetic, AMD, Infineon (formally known as Siemens), Matra and Dallas Semi-conductor. Q.4(a) Attempt any THREE of the following : [12] Q.4(a) (i) Describe following 8051 microcontroller instructions tions (a) SET B C (b) ADD (c) MOV A, #20H (d) XCH A, R0 (A) 8051 microcontroller instructions : (a) SET B C set carry flag (b) ADD Add indirect RAM to accumulator (c) MOV A, #20H Move immediate data to accumulator (d) XCH A, R0 Exchange register with accumulator Q.4(a) (ii) Draw the format of SCON register and describe the function of each bit. (A) SCON is a 8-bit register which indicates mode selection and flag generation of interrupt. Bit 7 Bit 0 SM 0 SM 1 SM 2 REN TB8 RB8 T1 R1 SM 0 and SM 1 : SM 0 SM 1 Modes 0 0 Serial mode 0 (synchronous comm) (10 bit asynchronous comm) Mode 3 SM 2 Use idmode for multiprocess communication REN (Received Enable) It is also referred as SCON.4. Since it is bit addressable. When REN bit is high it allows 8051 to receive data on RxD pin, by making REN = 0 the receiver is made disable. TB8 (Transfer bit 8) Use for serial modes 2 and 3. RB8 (Receive bit 8) Use for serial modes 2 and 3. T1 (Transmit Interrupt) When 8051 finishes transfer of 8 bit character it raises T1 flag to indicate that it is ready to transfer another byte. SM 1dy Vi1 0 10

11 Prelim Question Paper Solution R1 (Receive Interrupt) When 8051 receives data serially via RxD it raises R1 flag bit to indicate that a byte has been received. Q.4(a) (iii) Draw the circuit diagram of port 2 and describe its functions. (A) Port 2 can be configured as I/O port or higher order address bus depending upon the operation to be performed. Internal Data Bus Write to latch D Clk Read latch Q Q Addr Control Read pin I 1 I 0 2:1 MUX +V CC PORT 2 LINES AS AN ADDRESS BUS [A 8 -A 15 ] A 8 A 15 Control input should be 1. This input will be provided internally by 8051 depending upon the instruction i.e. memory related instructions. Thus, Control= 1, D FlipFlop will be isolated from mux, I 1 will be connected to o/p Y. When, address line = 0 then, I 1 = 0 y -= 0 and ouput of NOT Gate = 1 hence, it will turn ON transistor T (i.e. closed switch) Simultaneously, o/p of AND Gate = 0 as, address = 0 and Control = 1 this will turn OFF T (i.e. open switch) As T is off and T is ON current will start from Vcc and flows towards ground through R and T. Accordingly respective port line sinks the current and hence that respective addressing line will be treated as Logic O. When, address line = 1 then I 1 = 1 S 0 y T 1 T R pz.x an 11

12 : T.Y. Diploma MC Y = 1 and output of NOT Gate = O Hence, it will turn OFF transistor T (i.e. open swich) Simultaneously, o/p of AND Gate = 1 as, Address = 1 and Control = 0 this will turn ON T (i.e. closed switch) As T is ON and T is OFF current will start form Vcc and flow through T. Accordingly, respective port line sources the current and hence respective address line will be treated as logic 1. PORT 2 LINES AS I/O PORT: When, D = 1 clk = 1 Q = 1 Q = 0 But Q is connected to Mux Thus I 0 = 1 and o/p of NOT Gate = 0 Thus, T will turn OFF ( i.e. Open Switch) Therfore respective port line will source the current and Port2 X will be treated as Logic 1 When, D = 0 clk = 0 Q = 0 Q = 1 but Q is connected to MUX Thus I 0 = 0 and o/p of NOT Gate =1 Thus, T will turn ON (i.e. closed switch) Therefore respective port line will sink the current and pz.x will be treated as Logic 0. Q.4(a) (iv) State four instructions related with external memory. (A) Instructions related with external memory i) MOV M, r [[HL]] [ r ] Moves the content of register r to external memory location whose address is stored in HL register pair. e.g : MOV M, C This instruction moves the contents of register C into the memory location whose address is in HL register pair. 12

13 Width : 1 byte. Addressing : indirect addressing Flags affected : none Machine cycle : 2 (opcode fetch, memory write) T states : 7 (4 + 3) Prelim Question Paper Solution ii) MVI M, data 8 [[HL]] data 8 It moves the data specified in the instruction into the external memory location whose address is stored in HL register pair. e.g. MVI M, 50 H [[HL]] 50 H This instruction moves 50 H into memory location whose address is stored in HL register pair. Width : 2 bytes Addressing : immediate/indirect irect addressing. Flags affected : none. Machine cycle : 3 (opcode ode fetch, operand fetch, memory write) T states : 10 ( ) iii) LDA addr [A] [addr] It moves the contents of external memory location whose address is specified in the instruction into accumulator. e.g. LDA 3056 H [A] [3056 H] This instruction loads accumulator with the contents of memory location 3056 H. Width : 3 bytes Addressing : direct. Flags affected : none. Machine cycle : 4 (opcode fetch, operand fetch, operand fetch, memory read) T states : 13 ( ) iv) STA addr [addr] [A] It stores the contents of accumulator into the external memory location whose address is specified in the instruction. 13

14 : T.Y. Diploma MC e.g. STA 2560 H [2056 H] [A] This instruction stores the contents of accumulator into memory location 2056 H. Width : 3 bytes Addressing : direct addressing. Flags affected : none. Machine cycle : 4 (opcode fetch, operand fetch, operand fetch, memory write) T states : 13 ( ) Q.4(b) Attempt any ONE of the following : [6] Q.4(b) (i) Write a program to arrange number in ascending order using [6] 8051 instruction set. (A) Program : Arrange number in Ascending order Number are stored in memory from 30 to 3F H Arrange these numbers in Ascending order. 14

15 Prelim Question Paper Solution START : MOV R6, #0FH LOOP1 : MOV R0, #30H MOV R7, 06H (R 7 R 6 ) LOOP2 : MOV INC R0 CLRCu SUBB R0 JC SKIP MOV DEC R0 XCH INC R0 R0, A SKIP : DJNZ R7, LOOP 2 DJNZ R6, LOOP 1 HERE : LJMP HERE Q.4(b) (ii) Draw the interfacing diagram of stepper motor with 8051 microcontroller and write an assembly language program to rotate stepper motor continuously in clock wise direction. (A) Gnd +V CC C 1 = 33pf a(rst) V PP C MHz +V CC D 0.0 D 0.1 D 0.2 D 0.3 D 0.4 D 0.5 D 0.6 D C 2 = 33pf +V CC D 0 +V ULN 2003 Gnd V CC (+ 12V) Coil Rotor Coil [6] 15

16 : T.Y. Diploma MC UP : DELAY : YY : XX: ORG 0000H MOV A, # 33H MOV P1, A ACALL DELAY RR A SJMP UP MOV R4, # 0FFH MOV R5, # 0FFH DJNZ R5, XX DJNZ R4, YY RET END Q.5 Attempt any FOUR of the following : [16] Q.5(b) Draw and describe IE register of 8051 microcontroller. roller. (A) IE register can enable and disable various available interrupt EA ET2 ES ET1 EX1 ET0 EX0 EA (IE7) (IE6) ET2 (IE5) Disable all interrupts. If EA = 0, no interrupt is acknowledge if EA = 1 each interrupt source is individually enabled/ disabled by setting/clearing its enable bit Not implemented, reserved for future use Enables/Disables timer 2 for further use. E S (IE4) Enables/Disables serial port interrupt. ET1 (IE3) Enable/Disables timer / overflow interrupt. EX1 (IE2) Enable/Disables external interrupt 1. an ET0 (IE1) Enables/Disables timer o overflow interrupt. EX0 (IE0) Enables/Disables external interrupt o Q.5(b) Describe the timer modes of 8051 microcontroller. (A) Timer Modes of 8051 Microcontroller 8051 microcontroller has 4 timer modes. Timer modes can be selected with the help of TMOD register. 16

17 M 1 M 0 Timer Mode Mode 0 GATE INTX 0 0 Mode Mode Mode Mode 3 Prelim Question Paper Solution In mode 0, timer register is configured as 13 bit register, 8 bit for THX and 5 bit for TLX. Timer is enable when TRX = 1 and gate = 0 then register can hold values between 0000H to 1FFFH FFH in TH and TL. When register value reaches es its maximum it roles over to 0000H, when the register overflow it sets s timer interrupt flag TF one or zero. Mode 1 1 C Oscillator T a= = 0 12 THX TLX 8 bit 8 bit TFX Tx pin yac C T =act = 1 Overflow TRX GATE INTO In mode 1, timer register is configured as 16 bit register where 8 bit for THX and 8 bit for TLX and gate = 0, then registers can hold value between 0000H 0H to FFFFH FFFH in TH and TL. Mode 2 GATE INTO Oscillator Tx pin Oscillator Tx pin 1 12 TRX 1 12 TRX C T = 0 C T = 1 C T = 0 TLX C T = 1 8 bit THX 8 bit THX TLX 8 bit 5 bit TFX TFX 17

18 : T.Y. Diploma MC The operation is some for timer 0 and timer 1. In this mode, timer register is configured as TLX. When TLX overflows from FFH to 00H it sets the flag TFX and it loads THX. The reload leaves THX unchanged. In this mode timer 1 or timer 0 supports the automatic reload operation. The timer control logic is same as mode 0 or mode 1. Mode 3 GATE INTO Oscillator Oscillator 1 12 TRO 1 12 C T = 0 nk TLO TFO C T = 1 8 bit Overflow THO TF1 Timer 0 in mode 3 TL0 and TH0 are 2 separate registers as shown in figure. TL0 uses gate TR0, INT0 and TF0 control bit of timer 0 and TH0 uses TR1 and TF1 control bit of timer 1. When TL0 overflows from FFH to 00H, then it sets the timer flag TF0. If control bit TR1 is set, TH0 receives the timer clock. When counter TH0 overflows from FF to 00 then it sets the flag TF1. Timer 1 may still be used in mode 0/1/2 but it neither interrupt the processor sor nor sets the flag. When timer 0 is in mode 3, timer 1 can be used for baud rate generation in serial communication. Q.5(c) List the various interrupts in 8051 microcontroller along with their priorities and vector locations. (A) Various Interrupts in 8051 microcontroller Interrupt Location (ROM) Priority RESET 0000H Highest INT0 (external hardware) 0003H Timer 0 (TF0) 000BH ViInterrup ViRES VI VInt Int1 (external hardware) 0013H Timer 1 (TF1) 001BH Serial communication (R1/T1) 0023H Lowest TR1 an 18

19 Prelim Question Paper Solution Q.5(d) Write an assembly language program for 8051 microcontroller to generate square wave on P1.0 using delay subroutine. (A) ORG 0000H SET B P1.0 A CALL DELAY CLR P1.0 main : SJMP main END DELAY : MOV R 4, # 0FFH UP : DJNZ R4, UP RET Q.5(e) Draw the internal structure of port3 & list alternate functions of port3. (A) Structure of Port 3 : Internal Data Bus Write to latch D Read latch Q Q Alt output function [TXD, WR,laRD ] +V CC Read pin Alt input function [RXD, INTO, INT1, T 0, T 1 ] To configure PORT 3 as an input/output port the Alternate output function pin provided to NAND Gate will be Logic 1, done by microcontroller depending on the instruction. When D = 0, Q = 0, Then o/p of NAND Gate = 1, This will turn ON the transistor T i.e. closed switch. Accordingly, respective PORT 3 line will sink the current. This is treated as Logic 0 When D = 1 Q = 1, T R p3:x Real an W ya 19

20 : T.Y. Diploma MC Then o/p of NAND Gate = 0 This will turn OFF the transistor T i.e. open switch, Accordingly, respective PORT 3 pin will source current. This is treated as Logic 1. PORT 3 AS AN ALTERNATE FUNCTION PORT: To use the Alternate Functions of PORT 3, 8051 will set D input of D flipflop depending upon the instruction. Consider Alternate o/p function to NAND Gate is O Then, o/p of NAND Gate = 1 Accordingly, T will turn ON i.e. closed switch Respective PORT 3 line will be at Logic 0 Consider Alternate output function to NAND Gate is 1 Then, output of NAND Gate = 0 Accordingly, T will turn OFF i.e. open switch Respective PORT3 line will be at Logic 1 Q.6 Attempt any FOUR of the following : [16] Q.6(a) Write an assembly language age program to generate continuous square of 2KHz frequency on P1.4 using timer 0. Assume crystal frequency of 8051 microcontroller controller is MHz. (A) Given : Crystal frequency = MHz Timer input clock ck frequency = MHz = MHz 12 1 T = sec MHz Give frequency of output square wave is 2 KHz. Timer period of output square wave = 1 2KHz T sec. ON = T OFF = 500 = 250 sec. 2 Desire delay = 250 sec. Desired delay Desire count = Time period of input clock = = 230 Max. count Desire count = Timer count = (65306) 10 = (FFIA) h = 500 sec. 20

21 ORG 0000H MOV TMOD, # 01H CLR TR0 CLR TF0 UP : MOV TH0, # 0FFH MOV TL0, # 1AH SET B, TR0 here : JNB TF0 here CPL P1.4 CLR TF0 SJMP UP END ET2 (IE5) Enables/Disables timer 2 for further use. ES (IE4) Enables/Disables serial port interrupt. ET1 (IE3) Enables/Disables timer/overflow rflow interrupt. EX1 (IE2) Enables/Disables timer 0 overflow interrupt ET04 (IE1) Enables/Disables timer 0 overflow interrupt EX0 (IE0) Enables/Disables external interrupt 0 Prelim Question Paper Solution Q.6(b) Draw the format of TCON register and state the function of each bit. (A) TCON register This register er is 8-bit, bit addressable. It controls the timer/counter operation. First 4 bit indicates timer flag another 4 bit indicates interrupt flag. TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 Timer Interrupt TR0 and TR1 These flags are use to run the timer or ON/OFF the timer. TF1 and TF0 It indicates timer 1/0 overflow flag when timer/counter dytf0 overflows. IE1 / IE0 It indicates external interrupt 1/0. IT1 / IT0 It indicates timer 1/0 interrupt. When it is zero it is low level trigger for level 1 falling edge trigger. Q.6(c) Draw the control word register format of 8255 and describe the function of each bit. (A) Control Word Register Format of 8255 D 7 D 6 D 5 D 4 D 3 D 2 D 1 D 0 21

22 : T.Y. Diploma MC D 0 Port C (lower PC3 PC0) 1 = input 0 = output D 1 Port B, 1 = input 0 = output D 2 Mode select 0 = Mode0 1 = Mode1 D 3 Port C (Upper PC7 PC4) 1 = input 0 = output D 4 Port A, 1 = input 0 = output D 5 and D 6 Mode selection 00 Mode 0 01 Mode 1 10 Mode 2 D 7 1 = I/O port 0 = BSR mode Q.6(d) Draw and describe e IP register format of 8051 microcontroller. (A) IP register format of 8051 microcontroller By programming ming IP (Interrupt Priority) register we can assign higher priority to any one of the interrupt. bit = 1, higher priority bit = 0, lower priority PS PT1 PX1 PT0 PX0 (IP.7) Reserved (IP.6) Reserved (IP.5) Reserved PS (IP.4) Serial port interrupt priority bit PT1 (IP.3) timer 1 interrupt priority bit PX1 (IP.2) External interrupt 1 priority bit PT0(IP.1) Timer 0 interrupt priority bit PX0(IP.0) External interrupt 0 priority bit 22

23 Prelim Question Paper Solution Q.1(a) (v) Draw Block diagram of Discuss the operating modes of it. (A) Block diagram of IC 8255 The following is an overview of each of the three available modes: 1) MODE 0 (Basic Input/Output): put): Two eight bit ports and two 4 bit ports Any port can be either er input or output Outputs are latched Inputs are not latched 16 different Input/output configurations are possible in this mode. 2) MODE 1 (Strobed Input/output): Two Groups (Group A and Group B) Each group contains one 8 bit data port and (1) 4 bit control/data port The 8 bit data port can be either input or output Both inputs and outputs are latched The 4 bit port is used for control and status of the 8 bit data port 3) MODE 2 (Strobed Bidirectional Bus I/O): Used in Group A only One 8 bit bidirectional bus port (Port A ) and one (5) bit control port (port C) Both inputs and outputs are latched The 5 bit control port (Port C) is used for control and status for the (8) bit, bidirectional bus port (Port A) 23