CHW 469 : Embedded Systems

Transcription

1 CHW 469 : Embedded Systems Instructor: Dr. Ahmed Shalaby

2 I/O Ports in AVR The AVR microcontroller and embedded systems using assembly and c

3 Topics AVR pin out The structure of I/O pins I/O programming Bit manipulating

4 ATmega6/mega32 pinout. Vital Pins:. Power VCC Ground 2. Crystal XTAL XTAL2 3. Reset 2. I/O pins PORTA, PORTB, PORTC, and PORTD 3. Internal ADC pins AREF, AGND, AVCC +5 V +5 V 4 PIN DIP (XCK/T) PB (T) PB (INT2/AIN) PB2 (OC/AIN) PB3 (SS) PB4 (MOSI) PB5 (MISO) PB6 (SCK) PB MEGA PA (ADC) PA (ADC) PA2 (ADC2) PA3 (ADC3) PA4 (ADC4) PA5 (ADC5) PA6 (ADC6) PA7 (ADC7) RESET VCC GND AREF AGND AVCC +5 V XTAL2 XTAL (RXD) PD (TXD) PD (INT) PD2 (INT) PD3 (OCB) PD4 (OCA) PD5 (ICP) PD PC7 (TOSC2) PC6 (TOSC) PC5 (TDI) PC4 (TDO) PC3 (TMS) PC2 (TCK) PC (SDA) PC (SCL) PD7 (OC2)

5 The structure of IO pins Mega32/Mega6 (XCK/T) PB (T) PB (INT2/AIN) PB2 (OC/AIN) PB3 (SS) PB4 (MOSI) PB5 (MISO) PB6 (SCK) PB7 RESET VCC GND XTAL2 XTAL (RXD) PD (TXD) PD (INT) PD2 (INT) PD3 (OCB) PD4 (OCA) PD5 (ICP) PD DDRB PORTB PINB DDRx.n DDRA PORTA PINA PORTx.n PINx.n PA (ADC) PA (ADC) PA2 (ADC2) PA3 (ADC3) PA4 (ADC4) PA5 (ADC5) PA6 (ADC6) PA7 (ADC7) AREF AGND AVCC PC7 (TOSC2) PC6 (TOSC) PC5 (TDI) PC4 (TDO) PC3 (TMS) PC2 (TCK) PC (SDA) PC (SCL) PD7 (OC2)

6 The structure of IO pins Mega32/Mega6 (XCK/T) PB (T) PB (INT2/AIN) PB2 (OC/AIN) PB3 (SS) PB4 DDRx: (MOSI) PB5 PORTx: (MISO) PB6 PINx: (SCK) PB7 RESET VCC GND XTAL2 XTAL (RXD) PD (TXD) PD (INT) PD2 (INT) PD3 (OCB) PD4 (OCA) PD5 (ICP) PD DDRB PORTB PINB DDRA PORTA PINA Px7 Px6 Px5 Px4 Px3 Px2 Px Px DDRx.n PORTx.n PINx.n PA (ADC) PA (ADC) PA2 (ADC2) PA3 (ADC3) PA4 (ADC4) PA5 (ADC5) PA6 (ADC6) PA7 (ADC7) AREF AGND AVCC PC7 (TOSC2) PC6 (TOSC) PC5 (TDI) PC4 (TDO) PC3 (TMS) PC2 (TCK) PC (SDA) PC (SCL) PD7 (OC2)

7 The structure of IO pins Mega32/Mega6 (XCK/T) PB (T) PB (INT2/AIN) PB2 (OC/AIN) PB3 (SS) PB4 DDRx: (MOSI) PB5 PORTx: (MISO) PB6 PINx: (SCK) PB7 RESET VCC GND XTAL2 XTAL (RXD) PD (TXD) PD (INT) PD2 (INT) PD3 (OCB) PD4 (OCA) PD5 (ICP) PD DDRB PORTB PINB DDRA PORTA PINA Px7 Px6 Px5 Px4 Px3 Px2 Px Px DDRx.n PORTx.n PINx.n PA (ADC) PA (ADC) PA2 (ADC2) PA3 (ADC3) PA4 (ADC4) PA5 (ADC5) PA6 (ADC6) PA7 (ADC7) AREF AGND AVCC PC7 (TOSC2) PC6 (TOSC) PC5 (TDI) PC4 (TDO) PORTx PC3 (TMS) PC2 (TCK) DDRx PC (SDA) PC (SCL) PD7 (OC2) high impedance pull-up Out Out

8 Example Write a program that makes all the pins of PORTA one. (XCK/T) PB DDRA: PORTA:.INCLUDE M32DEF.INC LDI R2,xFF ;R2 = (binary) OUT PORTA,R2 ;PORTA = R2 OUT DDRA,R2 ;DDRA = R2 (T) PB (INT2/AIN) PB2 (OC/AIN) PB3 (SS) PB4 (MOSI) PB5 (MISO) PB6 (SCK) PB7 RESET VCC GND XTAL2 XTAL (RXD) PD (TXD) PD (INT) PD2 (INT) PD3 (OCB) PD4 (OCA) PD5 (ICP) PD6 Mega32/Mega6 PINB DDRB PORTB PINA DDRA PORTA PORTC DDRC PINC PA (ADC) PA (ADC) PA2 (ADC2) PA3 (ADC3) PA4 (ADC4) PA5 (ADC5) PA6 (ADC6) PA7 (ADC7) AREF AGND AVCC PC7 (TOSC2) PC6 (TOSC) PC5 (TDI) PC4 (TDO) PC3 (TMS) PC2 (TCK) PC (SDA) PC (SCL) PD7 (OC2) PORTx DDRx high impedance Out pull-up Out

9 Example 2 The following code will toggle all 8 bits of Port B forever with some time delay between on and off states: LDI R6,xFF ;R6 = xff = b OUT DDRB,R6 ;make Port B an output port ( ) L: LDI R6,x55 ;R6 = x55 = b OUT PORTB,R6 ;put x55 on port B pins CALL DELAY LDI R6,xAA ;R6 = xaa = b OUT PORTB,R6 ;put xaa on port B pins CALL DELAY RJMP L

10 Example 3 A 7-segment is connected to PORTA. Display on the 7-segment. DDRC : PORTC:.INCLUDE M32DEF.INC LDI R2,x6 ;R2 = (binary) OUT PORTC,R2 ;PORTC = R2 LDI R2,xFF ;R2 = (binary) OUT DDRC,R2 ;DDRC = R2 L: RJMP L ATmega32 PORTx PORTC DDRx high impedance Out pull-up Out 2

11 Example 4 A 7-segment is connected to PORTA. Display 3 on the 7-segment. DDR: PORTC:.INCLUDE M32DEF.INC LDI R2,x4F ;R2 = (binary) OUT PORTC,R2 ;PORTC = R2 LDI R2,xFF ;R2 = (binary) OUT DDRC,R2 ;DDRC = R2 L: RJMP L ATmega32 PORTx PORTC DDRx high impedance Out pull-up Out 2

12 Example 5: Input The following code gets the data present at the pins of port C and sends it to port B indefinitely, after adding the value 5 to it:.include "M32DEF.INC" LDI R6,x ;R6 = (binary) OUT DDRC,R6 ;make Port C an input port LDI R6,xFF ;R6 = (binary) OUT DDRB,R6 ;make Port B an output port( for Out) L2: IN R6,PINC ;read data from Port C and put in R6 LDI R7,5 ADD R6,R7 ;add 5 to it OUT PORTB,R6 ;send it to Port B RJMP L2 ;continue forever

13 Pull-up resistor vcc PORTx.n = Close = Open pin n of port x PINx.n Outside the AVR chip Inside the AVR chip

14 The structure of I/O pins P PUD RDx Q D DDRxn Q CLK DATA BUS WR DDRxn Pxn Sleep DDRx.n PORTx.n PINx.n SYNCHRONIZER Q RESET RRx OUTPUT D PORTxn Q CLK INPUT RESET WR PORTxn N D L Q Q D Q PINxn Q RPx RESET RESET CLK I/O

15 Example 6 Write a program that continuously sends out to Port C the alternating values of x55 and xaa..include "M32DEF.INC" LDI R6,xFF ;R6 = (binary) OUT DDRC,R6 ;make Port C an output port L: LDI R6,x55 ;R6 = x55 OUT PORTC,R6 ;put x55 on Port C pins LDI R6,xAA ;R6 = xaa OUT PORTC,R6 ;put xaa on Port C pins RJMP L

16 The structure of IO pins PORTx DDRx high impedance pull-up Out Out P PUD RDx Q D DDRxn Q CLK DATA BUS WR DDRxn RESET RRx Pxn Sleep Q D PORTxn Q CLK WR PORTxn SYNCHRONIZER RESET N D L Q Q D Q PINxn Q RPx RESET RESET CLK I/O

17 Input (Tri-state vs. pull up) P PUD RDx Pull-up Resistor Q D DDRxn Q CLK WR DDRxn DATA BUS RESET RRx Pxn Sleep Q D PORTxn Q RESET CLK WR PORTxn SYNCHRONIZER D Q D Q N L PINxn Q Q RESET RESET CLK I/O RPx The while the represents how the content of PORTx register affects the pull-up resistor; shows how a data can be read from a pin

18 Example 7 4 PIN DIP Write a program that reads from port A and writes it to port B..INCLUDE M32DEF.INC LDI R2,x OUT DDRA,R2 ;DDRA = R2 ;R2 = (binary) LDI R2,xFF ;R2 = (binary) OUT DDRB,R2 ;DDRB = R2 L: IN R2,PINA ;R2 = PINA (XCK/T) PB (T) PB (INT2/AIN) PB2 (OC/AIN) PB3 (SS) PB4 (MOSI) PB5 (MISO) PB6 (SCK) PB7 RESET VCC GND XTAL2 XTAL (RXD) PD (TXD) PD (INT) PD2 (INT) PD3 (OCB) PD4 (OCA) PD5 (ICP) PD MEGA PA (ADC) PA (ADC) PA2 (ADC2) PA3 (ADC3) PA4 (ADC4) PA5 (ADC5) PA6 (ADC6) PA7 (ADC7) AREF AGND AVCC PC7 (TOSC2) PC6 (TOSC) PC5 (TDI) PC4 (TDO) PC3 (TMS) PC2 (TCK) PC (SDA) PC (SCL) PD7 (OC2) OUT PORTB,R2 ;PORTB = R2 RJMP L PORTx DDRx high impedance pull-up Out Out

19 I/O bit manipulation programming

20 SBI and CBI instructions SBI (Set Bit in IO register) SBI ioreg, bit ;ioreg.bit = Examples: SBI PORTD, ;PORTD. = SBI DDRC,5 ;DDRC.5 = CBI (Clear Bit in IO register) CBI ioreg, bit ;ioreg.bit = Examples: CBI PORTD, ;PORTD. = CBI DDRC,5 ;DDRC.5 =

21 Example Write a program that toggles PORTA.4 continuously..include M32DEF.INC SBI DDRA,4 L: SBI PORTA,4 CBI PORTA,4 RJMP L

22 Example An LED is connected to each pin of Port D. Write a program to turn on each LED from pin D to pin D7. Call a delay module before turning on the next LED..INCLUDE "M32DEF.INC" LDI R2, xff OUT DDRD, R2 ;make PORTD an output port SBI PORTD, ;set bit PD CALL DELAY ;delay before next one SBI PORTD, ;turn on PD CALL DELAY ;delay before next one SBI PORTD,2 ;turn on PD2 CALL DELAY SBI PORTD,3 CALL DELAY SBI PORTD,4 CALL DELAY SBI PORTD,5 CALL DELAY SBI PORTD,6 CALL DELAY SBI PORTD,7 CALL DELAY

23 SBIC and SBIS SBIC (Skip if Bit in IO register Cleared) SBIC ioreg, bit ; if (ioreg.bit = ) skip next instruction Example: SBIC PORTD, ;skip next instruction if PORTD.= INC LDI R2 R9,x23 SBIS (Skip if Bit in IO register Set) SBIS ioreg, bit ; if (ioreg.bit = ) skip next instruction Example: SBIS PORTD, ;skip next instruction if PORTD.= INC LDI R2 R9,x23

24 Example Write a program to perform the following: (a) Keep monitoring the PB2 bit until it becomes HIGH; (b) When PB2 becomes HIGH, write value $45 to Port C, and also send a HIGH-to-LOW pulse to PD3..INCLUDE "M32DEF.INC" CBI DDRB, 2 SBI PORTB,2 LDI R6, xff OUT DDRC, R6 SBI DDRD, 3 AGAIN: SBIS PINB, 2 RJMP AGAIN LDI R6, x45 OUT PORTC, R6 SBI PORTD, 3 CBI PORTD, 3 HERE: RJMP HERE ;make PB2 an input ;make Port C an output port ;make PD3 an output ;Skip if Bit PB2 is HIGH ;keep checking if LOW ;write x45 to port C ;set bit PD3 (H-to-L) ;clear bit PD3

25 Example A switch is connected to pin PB and an LED to pin PB7. Write a program to get the status of SW and send it to the LED. 4.7k Switch VCC PB AVR PB7 27 LED.INCLUDE "M32DEF.INC" CBI DDRB, SBI DDRB,7 AGAIN: SBIC PINB, RJMP OVER CBI PORTB,7 RJMP AGAIN OVER: SBI PORTB,7 RJMP AGAIN ;make PB an input ;make PB7 an output ;skip next if PB is clear ;(JMP is OK too) ;we can use JMP too ;we can use JMP too

26 Arithmetic and Logic Chapter 5 The AVR microcontroller and embedded systems using assembly and c

27 Objectives The concept of signed numbers and 2 complement Addition and subtraction instructions Carry and overflow Logical instruction and masking Compare instruction and branching Shift, Rotate and Data serialization BCD, Packed BCD and ASCII conversion.

28 34 =? =? 34 = (99-34) + Some ideas 34 9 =? = 34 + (99-9)+ -

29 =? = + =A = + A =

30 ADD instructions ADD Rd,Rr ;Rd = Rd + Rr ( Direct or immediate are not supported)

31 ADD instructions ADD Rd,Rr ;Rd = Rd + Rr ( Direct or immediate are not supported)

32 ADC instructions

33 SUB instruction SUB Rd,Rr ;Rd = Rd - Rr ( immediate are not supported) SUB Rd,Rr ; Rd = Rd K

34 SBC instruction SBC Rd,Rr ;Rd = Rd Rr-C ( immediate are not supported) SBIc Rd,Rr ;Rd = Rd K-C (H) - 96 (H) CC (H)

35 Multiplication and Division

36 Logic Instructions AND Rd,Rr ;Rd = Rd AND Rr OR Rd,Rr ;Rd = Rd OR Rr EOR Rd,Rr ;Rd = Rd XOR Rr ( immediate are not supported) COM Rd,Rr ;Rd = Complement of Rd ( Rd) NEG Rd,Rr ;Rd = 2 Complement of Rd ( Rd) AND is used to clear an specific bit/s of a byte OR is used to set an specific bit/s of a byte

37 Setting and Clearing bits AND Rd,Rr ;Rd = Rd AND Rr OR Rd,Rr ;Rd = Rd OR Rr EOR Rd,Rr ;Rd = Rd XOR Rr ( immediate are not supported) COM Rd,Rr ;Rd = Complement of Rd ( Rd) NEG Rd,Rr ;Rd = 2 Complement of Rd ( Rd) AND is used to clear an specific bit/s of a byte OR is used to set an specific bit/s of a byte AND OR

38 Branch and CP Instructions CP Rd,Rr ;Rd Rr (only flags are set) BRVC is used to branch when overflow is clear to zero BRVS is used to branch when overflow is set to one

39 ROR instruction ROR Rd ;Rd (only flags are set) In ROR, as bits are rotated from left to right, the carry flag enters the MSB and the LSB exits to the carry flag. In other words, in ROR the C is moved to the MSB, and the LSB is moved to the C. See what happens to after running 3 ROR instructions: CLC ;make C = (carry is ) LDI R2, x26 ;R2 = ROR R2 ;R2 = C = ROR R2 ;R2 = C = ROR R2 ;R2 = C =

40 ROL instruction ROR Rd ;Rd (only flags are set) ROL. In ROL, as bits are shifted from right to left, the carry flag enters the LSB and the MSB exits to the carry flag. In other words, in ROL the C is moved to the LSB, and the MSB is moved to the C. SEC ;make C = (carry is ) LDI R2,x5 ;R2 = ROL R2 ;R2 = C = ROL R2 ;R2 = C = ROL R2 ;R2 = C = ROL R2 ;R2 = C =

41 LSL instruction LSL Rd ;logical shift left In LSL, as bits are shifted from right to left, enters the LSB and the MSB exits to the carry flag. In other words, in LSL is moved to the LSB, and the MSB is moved to the C. this instruction multiplies content of the register by 2 assuming that after LSL the carry flag is not set. In the next code you can see what happens to after running 3 LSL instructions. CLC ;make C = (carry is ) LDI R2, x26 ;R2 = (38) c = LSL R2 ;R2 = (74) C = LSL R2 ;R2 = (48) C = LSL R2 ;R2 = (98) C = as C= and content of R2 ;is not multiplied by 2

42 ROR Rd ;Rd (only flags are set) In LSR, as bits are shifted from left to right, enters the MSB and the LSB exits to the carry flag. In other words, in LSR is moved to the MSB, and the LSB is moved to the C. this instruction divides content of the register by 2 and carry flag contains the remainder of division. In the next code you can see what happens to after running 3 LSL instructions. LDI R2,x26 ;R2 = (38) LSR R2 ;R2 = (9) C = LSR R2 ;R2 = (9) C = LSR R2 ;R2 = (4) C =

43 ASR Instruction ROR Rd ;Rd (only flags are set) ASR means arithmetic shift right. ASR instruction can divide signed number by 2. In LSR, as bits are shifted from left to right, MSB is held constant and the LSB exits to the carry flag. In other words MSB is not changed but is copied to D6, D6 is moved to D5, D5 is moved to D4 and so on. In the next code you can see what happens to after running 5 ASL instructions. LDI R2, D6 ;R2 = (-48) c = LSL R2 ;R2 = (-24) C = LSL R2 ;R2 = (-2) C = LSL R2 ;R2 = (-6) C = LSL R2 ;R2 = (-3) C = LSL R2 ;R2 = (-) C =

44 BCD, Packed BCD and ASCII conversion. ASCII BCD Codes Packed BCD BCD Codes BCD BCD ASCII and BCD Codes for Digits 9

45 Packed BCD to ASCII conversion To convert packed BCD to ASCII: you must first convert it to unpacked BCD. Then the unpacked BCD is tagged with (3H). Packed BCD = Un packed BCD =, ACSII =,

46 Advanced Assembly Chapter 6 The AVR microcontroller and embedded systems using assembly and c

47 Topics Assembler directives Addressing modes Macro EEPROM memory Checksum

48 Some Assembler directives Example + LDI R2,5+3 ;LDI R2,8 - LDI R3,9-3 ;LDI R3,6 * LDI R25,5*7 ;LDI R25,35 / LDI R9,8/2 ;LDI R9,4 Example & LDI R2,x5&x ;LDI R2,x LDI R25,x5 x ;LDI R25,x5 ^ LDI R23,x5^x ;LDI R23,x4 Example << LDI R6, x<< ;LDI R6,x2 >> LDI R6, x8 >>2 ;LDI R6,x2

49 HIGH and LOW LDI LDI R2, LOW(x234) R2, HIGH(x234) LDI R2, $34 LDI R2, $2 $234 HIGH LOW LDI R2, LOW(-2) LDI R2, $FF LDI R2, HIGH(-2) LDI R2, $38-2 = $FF38 HIGH LOW

50 Single Register Addressing Mode Single Register Addressing Mode INC Rd INC R9 DEC Rd DEC R23 ;R23 = R23 2 bits Op. Code 4 bits Rd GPRs d 3

51 Immediate Addressing Mode (Single register with immediate) 4 bits Op. Code 8 bits Immediate 4 bits Rd GPRs LDI Rd,K LDI R9,25 SUBI Rd,K SUBI R23,5 ;R23 = R23 5 d 3 ANDI Rd,K ANDI R2,x5

52 Two-register addressing mode 6 bits Op. Code 5 bits Rr 5 bits Rd GPRs d r ADD Rd,Rr ADD R26,R23 SUB Rd,Rr LDI R2,R 3

53 Direct addressing mode LDS Rd,address LDS R9,x33 STS address,rs STS x95,r Op. Code Rr/Rd Data Address 6 5 Data Space Note: RAMEND has been used to represent the highest location in data space. RAMEND

54 I/O direct addressing mode OUT address, Rs OUT x7,r6 IN Rs,address IN R9,x9 5 Op. Code Rr/Rd 5 A I/O Memory A 63

55 Register indirect addressing mode LD Rd,X Data Space LD R24,X 5 X, Y, OR Z - REGISTER LD R9,Y LD R2,Z ST X,Rd ST X,R8 ST Y,R2 Note: RAMEND has been used to represent the highest location in data space. RAMEND 5 XH XL X register : 7 7 R27 R26 5 YH YL Y register : 7 7 R29 R28 5 ZH ZL Z register : 7 7 R3 R3

56 Example Write a program to copy the value $55 into memory locations $4 to $44 LDI R9,x5 ;R9 = 5 (R9 for counter) LDI R6,x55 ;load R6 with value x55 (value to be copied) LDI YL,x4 ;load the LDI low byte YL,LOW(x4) of Y with value x4 LDI YH,x ;load the LDI high YH,HIGH(x4) byte of Y with value x L: ST Y,R6 ;copy R6 to memory location x4 INC YL ;increment the low byte of Y DEC R9 ;decrement the counter BRNE L ;loop until counter = zero

57 Auto-increment and Auto decrement Register indirect addressing with Post-increment LD Rd, X+ 5 X, Y, OR Z - REGISTER Data Space LD R2,X+ ST X+, Rs ST X+, R8 + RAMEND Register indirect addressing with Pre-decrement LD Rd, -X 5 X, Y, OR Z - REGISTER Data Space LD R9,-X ST X,R3 - + RAMEND

58 Example Write a program to copy the value $55 into memory locations $4 to $444 LDI R9,x5 ;R9 = 5 (R9 for counter) LDI R6,x55 ;load R6 with value x55 (value to be copied) LDI YL,LOW($4) ;load the low byte of Y with value x4 LDI YH,HIGH($4) ;load the high byte of Y with value x L: ST Y+,R6 ;copy R6 to memory location Y DEC R9 ;decrement the counter BRNE L ;loop until counter = zero

59 Register indirect with displacement STD Z+q,Rr ;store Rr into location Z+q STD Z+5,R2 ;store R2 in location Z+5 LDD Rd, Z+q ;load from Z+q into Rd LDD R2, Z+8 ;load from Z+8 into R2 5 Y OR Z - REGISTER Data Space + 5 Op. 5 Rr/Rd 6 5 q RAMEND

60 Storing fixed data in flash memory DATA:.DB 28 ;DECIMAL(C in hex) DATA2:.DB b ;BINARY (35 in hex) DATA3:.DB x39 ;HEX DATA4:.DB 'Y' ;single ASCII char DATA6:.DB "Hello ALI";ASCII string

61 Storing fixed data in flash memory LPM Rd, Z LPM R5, Z Example: LDI R3,x8 LDI R3, LPM R8,Z ;read from the low byte of loc x4 LPM Rd, Z+ LPM R2,Z Program Memory 5 LSB Z - REGISTER FLASHEND

62 Storing fixed data in flash memory LPM Rd, Z LPM R5, Z Example: LDI R3,x8 LDI R3, Low High Address $ $ $ LPM R8,Z ;read from the low byte of loc x4 LPM Rd, Z+ LPM R2,Z Program Memory 5 LSB Z - REGISTER 5 5 Low High Address $2 $3 8 7 $ $4 $5 $2 $6 $7 $3 $8 $9 $4 $A $B $5 FLASHEND.... $FFFC $FFFD $7FFE $FFFE $FFFF $7FFF

63 Example Analyze the following program; then rewrite it using LPM R2,Z+.ORG $ ;burn into ROM starting at LDI R2,xFF OUT DDRB,R2 ;make PB an output LDI ZL, LOW(MYDATA<<) ;ZL = look-up table low-byte addr LDI ZH,HIGH(MYDATA<<) ;ZH = A look-up table high-byte addr LPM R2,Z LPM R2,Z+ OUT PORTB,R2 ;send it OUT to Port BPORTB,R2 INC ZL ;R3 = pointing to next byte (A) LPM R2,Z ;load R2 LPMwith 'S' R2,Z+ char pointed to by Z OUT PORTB,R2 ;send it OUT to Port BPORTB,R2 INC ZL ;R3 = 2 pointing to next (A2) LPM R2,Z ;load R2 with 'A' char pointed to by Z OUT PORTB,R2 ;send it to Port B HERE: RJMP HERE ;stay here forever ;data is burned into code(program) space starting at $5.ORG $5 MYDATA:.DB "USA"

64 Example Assume that ROM space starting at $5 contains the message The Promise of World Peace. Write a program to bring it into CPU one byte at a time and place the bytes in RAM locations starting at $4..ORG ;burn into ROM starting at LDI ZL, LOW(MYDATA<<) ;R3 = low-byte addr LDI ZH, HIGH(MYDATA<<) ;R3 = A, high-byte addr LDI XL, LOW(x4) ;R26 = 4, low-byte RAM address LDI XH, HIGH(x4) ;R27 =, high-byte RAM address AGAIN: LPM R6, Z+ ;read the table, then increment Z CPI R6, ;compare R6 with BREQ END ;exit if end of string ST X+, R6 ;store R6 in RAM and inc X RJMP AGAIN END: RJMP END.ORG x5 ;data burned starting at x5 MYDATA:.DB "The Promise of World Peace",

65 Macro.MACRO INITSTACK LDI R6,HIGH(RAMEND) OUT SPH,R6 LDI R6,LOW(RAMEND) OUT SPL,R6.ENDMACRO INITSTACK

66 Macro.MACRO LOADIO LOADIO DDRB,xFF LOADIO PORTB,x55

67 EEPROM EEPROM is a place to store data. It is not deleted when power is off ATmega32 has 24 bytes of EEPROM In AVR 3 registers are dedicated to EEPROM EEARH:EEARL EEDR EECR Bit EEARH EEARL Bit 5 - EEAR7 7 EEPROM Address Register 4 5 EEARH EEARL - EEAR EEAR EEAR4 4 - EEAR3 3 - EEAR2 2 9 EEAR9 EEAR 8 EEAR8 EEAR EECR EEDR EEPROM 23

68 EEPROM EEPROM is a place EEPROM to Data store Register data. It is not deleted when power is off ATmega32 has 24 bytes of EEPROM In AVR 3 registers are dedicated to EEPROM EEARH:EEARL EEDR EECR Bit EEARH EEARL Bit 5 - EEAR7 7 EEPROM Address Register 4 5 EEARH EEARL - EEAR EEAR EEAR4 4 - EEAR3 3 - EEAR2 2 9 EEAR9 EEAR 8 EEAR8 EEAR EECR EEDR EEPROM 23

69 EEPROM EEPROM is a place EEPROM to Data store Register data. It is not deleted when power is EEPROM off Control Register ATmega32 has 24 bytes of EEPROM In AVR 3 registers are dedicated to EEPROM EEARH:EEARL EEDR EECR Bit EEARH EEARL Bit 5 - EEAR7 7 EEPROM Address Register 4 5 EEARH EEARL - EEAR EEAR EEAR4 4 - EEAR3 3 - EEAR2 2 9 EEAR9 EEAR 8 EEAR8 EEAR EECR EEDR EEPROM 23

70 Reading from EEPROM. Wait until EEWE becomes zero. 2. Write new EEPROM address to EEAR (optional) 3. Set EERE to one. 4. Read EEPROM data from EEDR.

71 Writing into EEPROM. Wait until EEWE becomes zero. 2. Write new EEPROM address to EEAR (optional). 3. Write new EEPROM data to EEDR (optional). 4. Set EEMWE bit to one. 5. Within four clock cycles after setting EEMWE, set EEWE to one.

72 Writing into EEPROM. Wait until EEWE becomes zero. 2. Write new EEPROM address to EEAR (optional). 3. Write new EEPROM data to EEDR (optional). 4. Set EEMWE bit to one. 5. Within four clock cycles after setting EEMWE, set EEWE to one.

73 Checksum To detect data corruption Calculating checksum byte: Add the bytes together and drop the carries Take the 2 s complement of the total sum Testing checksum Add the bytes together and drop the carries Add the checksum byte to the sum If the result is not zero, data is corrupted

74 Example Find the checksum byte for the followings: $25, $62, $3F, $52 Solution: $25 + $62 + $3F + $52 $ 8 Checksum byte = 2 s complement of $8 = $E8

75 Example The checksum byte is $E8. Test checksum for the following data: Solution: $25, $62, $3F, $52 $25 + $62 + $3F + $52 + $E8 $ not corrupted