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XMODEM RECEIVE ROUTINE

                                    ;***************************************************************************
                                    ;
                                    ; File Name		:'xmodem.asm"
                                    ; Title			:XMODEM only receive
                                    ; Date			:2002.07.03.
                                    ; Version		:1.0.0
                                    ; Support telephone	:+36-70-333-4034, Old: +36-30-9541-658
                                    ; Support fax		:
                                    ; Support Email		:info@vfx.hu
                                    ; Target MCU		:AT90S8515
                                    ;
                                    ;***************************************************************************
                                    ;	D E S C R I P T I O N
                                    ;
                                    ;
                                    ;
                                    ;***************************************************************************
                                    ;	M O D I F I C A T I O N   H I S T O R Y
                                    ;
                                    ;
                                    ;       rev.      date      who  why
                                    ;	----	----------  ---	--------------------------------------------
                                    ;	0.01	2002.07.03  VFX	Creation
                                    ;
                                    ;
                                    ;***************************************************************************
                                    ;Hardware
                                    ;***************************************************************************
                                    ;*
                                    ;*	Kvarc: f=7.3728 MHz (T=135.63368 ns)
                                    ;*
                                    ;***************************************************************************
                                    ;
                                    ;
                                    ;
                                    
                                    ;***************************************************************************
                                    ;* Const Def
                                    
                                    .EQU	Xmodem_Sync	=	0	;szinkronizalasi fazis
                                    .EQU	Xmodem_SOH	=	1	;SOH byte-ra var
                                    .EQU	Xmodem_Fill	=	2	;SOH byte megjott, block init megvolt
                                    .EQU	Xmodem_Err	=	3	;megszakadt az atvitel, NAK kuldese 3 masodpercenkent
                                    
                                    
                                    .EQU	SyncTiming	=	300	;ket karakter elkuldese kozott
                                    					;eltelt ido szinc. uzemmodban 3sec @100Hz
                                    
                                    
                                    ;**************************************************************************
                                    ;* Hardware Def.
                                    ;
                                    
                                    
                                    ;***************************************************************************
                                    ;**** VARIABLES
                                    .DSEG
                                    
                                    
                                    CRC:		.BYTE	2		; CRC for XMODEM
                                    XmodemFlag:	.BYTE	1		;Xmodem Flag
                                    					;[2:0] = 000 sending 'c' Phase 1: syncronize
                                    
                                    Xm_BlkCounter:	.BYTE	1		;Xmodem Block Counter [00-FF]
                                    XmodemPTR:	.BYTE	1		;Xmodem Buffer pointer
                                    XmodemBuf:	.BYTE	133		;XMODEM RxBuffer
                                    FileLength:	.byte	4		;File hossz 32 bites
                                    LastPocketSize:	.byte	1		;utolso pocket merete byte-ban [0...128]
                                    XmodemMode:	.byte	1		;Mode0 - Nul modem letolti de nem csinal semmit
                                    					;Mode1 - DSP Boot
                                    Xm_ErrorCNT:	.byte	1		;Xmodem Time to Abort counter
                                    
                                    ;***************************************************************************
                                    .ESEG
                                    
                                    
                                    ;***************************************************************************
                                    .CSEG
                                    
                                    
                                    ;***************************************************************************
                                    ;** Init Xmodem File Receive
                                    ;**
                                    
                                    Init_Xmodem:    ldi	R16,128
                                    		sts	LastPocketSize,R16
                                    		clr	R0
                                    		sts	FileLength+0,R0
                                    		sts	FileLength+1,R0
                                    		sts	FileLength+2,R0
                                    		sts	FileLength+3,R0
                                    		sts	Xm_ErrorCNT,R0
                                    		sts	XmodemFlag,R0
                                    		sts	Xm_BlkCounter,R0
                                    Init_XmNextBl:	clr	R0
                                    		sts	CRC+0,R0
                                    		sts	CRC+1,R0
                                    		sts	XmodemPTR,R0
                                    		STS	SCNT2+0,R0
                                    		STS	SCNT2+1,R0
                                    		ret
                                    
                                    
                                    ;***************************************************************************
                                    ;** Calc & Update XMODEM CRC
                                    ;*
                                    ;* In: R0 - data byte
                                    
                                    
                                    UpdateCRC:      lds     R17,CRC+1
                                    		mov     R15,R17
                                    		swap    R17
                                    		mov     R16,R17
                                    
                                    		eor     R17,R15
                                    		andi    R17,0xF0
                                    		andi    R16,0x0F
                                    		eor     R15,R16
                                    
                                    		mov     R14,R17
                                    		lsl     R14
                                    		rol     R16
                                    
                                    		eor     R15, R14
                                    		eor     R17,R16
                                    
                                    		lds     R14,CRC+0
                                    		eor     R15,R0
                                    		eor     R17,R14
                                    
                                    		sts     CRC+0,R15
                                    		sts     CRC+1,R17
                                    		ret
                                    
                                    
                                    ;***************************************************************************
                                    ;** XMODEM Receive File & Block
                                    ;*
                                    ;*
                                    Xmodem_Rec:    	lds	R16,XmodemFlag
                                    		cpi	R16,Xmodem_Sync
                                    		breq	Xm_Sync
                                    
                                    		cpi	R16,Xmodem_Fill
                                    		brne	Xmodem_Rec1
                                    		rjmp	Xm_Fill
                                    
                                    Xmodem_Rec1:	cpi	R16,Xmodem_SOH
                                    		breq	Xm_SOH
                                    
                                    		cpi	R16,Xmodem_Err
                                    		breq	Xm_Sync
                                    
                                    
                                    		rjmp	Xmodem_Cancel
                                    
                                    
                                    Xm_Sync:	call	Rs232GetByte
                                    		brcs	Xm_valamijott
                                    						;itt meg mindig nem jott semmi
                                    		lds	R16,SCNT2+0
                                    		lds	R17,SCNT2+1
                                    		or	R16,R17			;Timer lejart?
                                    		breq	Xm_Sync1
                                    		ret
                                    
                                    Xm_Sync1:	ldi	R16,NAK			;akkor, ha hiba van  NAK megy 3 masodpercenkent
                                    		lds	R17,XmodemFlag
                                    		cpi	R17,Xmodem_Err
                                    		breq	Xm_Sync2
                                    
                                    						;mivel meg mindig nem jott semmi kuldunk egy
                                    						;CRC - karaktert 3 masodpercenkent
                                    
                                    		lds	R16,Xm_ErrorCNT		;ha 20 'C' ideig nem jon semmi akkor abort!!!
                                    		inc	R16
                                    		sts	Xm_ErrorCNT,R16
                                    		cpi	R16,20
                                    		brne	Xm_Sync25
                                    		rjmp	Xm_Abort
                                    
                                    Xm_Sync25:	ldi	R16,'C'
                                    
                                    
                                    Xm_Sync2:	call	SendChrW
                                    		ldi	R16,Low(SyncTiming)	;Timer=3sec @100Hz
                                    		sts	SCNT2+0,R16
                                    		ldi	R17,High(SyncTiming)
                                    		sts	SCNT2+1,R17
                                    		ret
                                    
                                    
                                    Xm_SOH:		call	Rs232GetByte
                                    		brcs	Xm_valamijott
                                    		ret
                                    
                                    Xm_valamijott:	mov	R16,R0
                                    		cpi	R16,CAN
                                    		breq	Xmodem_Cancel
                                    		cpi	R16,SOH
                                    		breq	Xmodem_StartOfH
                                    		cpi	R16,EOT
                                    		breq	Xmodem_EndOfT
                                                    rjmp	Xmodem_Rec
                                    
                                    
                                    Xm_ByteStr:	.db	" Bytes received ",CR,0
                                    
                                    						;End of Trans == Canacel
                                    Xmodem_EndOfT:
                                    		ldi	R16,ACK
                                    		call	SendChrW		;Pozitiv nyugta
                                    
                                    Xm_Abort:	ldi	R16,CR
                                    		call	SendChrW		;soremeles
                                    
                                    		lds	R16,FileLength+0	;ACC1 LSByte
                                    		lds	R17,FileLength+1
                                    		lds	R18,FileLength+2
                                    		lds	R19,FileLength+3
                                      		call	ULTOA			;Print FileLength
                                    
                                    		ldi	XL,low(ASCIIBuf)	;Ascii Buffer Ptr
                                    		ldi	XH,high(ASCIIBuf)
                                    						;ldi	R22,12
                                       		call	PrintASCII		;rcall	DumpASCII
                                    
                                    		ldi	R16,Low(Xm_ByteStr)
                                    		ldi	R17,High(Xm_ByteStr)
                                    		call	SendStrW
                                    
                                    
                                    Xmodem_Cancel:	lds	R16,Term_Stat		;End of Xmodem receiving
                                    		cbr	R16,Term_Rec_Xmodem	;Normal Terminal Mode
                                    		sts	Term_Stat,R16
                                    
                                    		lds	R17,XmodemMode
                                    		cpi	R17,1
                                    		brne	Xm_CancelEnd
                                    						;itt lesz vege a FALSH update-nak
                                    
                                    Xm_CancelEnd:	clr	R17
                                    		sts	Updating,R17		;Ezel jelzzuk keszen vagyunk
                                    		sts	XmodemMode,R17		;barmi volt is, most null modem
                                    		jmp	CMDOk
                                    
                                    
                                    
                                    Xmodem_StartOfH:
                                    		ldi	R16,Xmodem_Fill
                                    		sts	XmodemFlag,R16
                                    		rcall	Init_XmNextBl
                                    		ldi	ZL,Low(SyncTiming)	;Timer=3sec @100Hz
                                    		sts	SCNT2+0,ZL		;he nem jon ujjab byte, akkor baj van!!
                                    		ldi	ZL,High(SyncTiming)
                                    		sts	SCNT2+1,ZL
                                    		rjmp	Xmodem_Rec
                                    
                                    
                                    Xm_Fill:	call	Rs232GetByte		;itt beolvasunk 132 byte-ot
                                    		brcs	Xm_data			; blk counter,255-blk counter [2 byte]
                                    						; adatblok [128 byte]
                                    						; CRC [2 byte]
                                    						;total 132 byte
                                    
                                    		lds	R16,SCNT2+0		;he nem jon ujjab byte, akkor baj van!!
                                    		lds	R17,SCNT2+1
                                    		or	R16,R17
                                    		brne	Xm_vanido
                                    
                                    		ldi	R16,Xmodem_Err
                                    		sts	XmodemFlag,R16		;Time Out, Ismetles kell
                                    
                                    Xm_vanido:	ret
                                    
                                    Xm_data:
                                    		ldi	ZL,Low(SyncTiming)	;Timer=3sec @100Hz
                                    		sts	SCNT2+0,ZL		;he nem jon ujjab byte, akkor baj van!!
                                    		ldi	ZL,High(SyncTiming)
                                    		sts	SCNT2+1,ZL
                                    
                                    		ldi	ZL,Low(XmodemBuf)
                                    		ldi	ZH,High(XmodemBuf)
                                    		clr	R1
                                    		lds	R16,XmodemPTR
                                    		add	ZL,R16
                                    		adc	ZH,R1			;ZL:ZH -> Xmodem Actualis Pos.
                                    		st	Z,R0			;Char eltarolasa
                                    		inc	R16
                                    		sts	XmodemPTR,R16
                                             	cpi	R16,3			;3
                                 

Programming the AVR Microcontrollers in Assember Machine Language

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Atmel AVR From Wikipedia, the free encyclopedia (Redirected from Avr) Jump to: navigation, search The AVRs are a family of RISC microcontrollers from Atmel. Their internal architecture was conceived by two students: Alf-Egil Bogen and Vegard Wollan, at the Norwegian Institute of Technology (NTH] and further developed at Atmel Norway, a subsidiary founded by the two architects. Atmel recently released the Atmel AVR32 line of microcontrollers. These are 32-bit RISC devices featuring SIMD and DSP instructions, along with many additional features for audio and video processing, intended to compete with ARM based processors. Note that the use of "AVR" in this article refers to the 8-bit RISC line of Atmel AVR Microcontrollers. The acronym AVR has been reported to stand for Advanced Virtual RISC. It's also rumoured to stand for the company's founders: Alf and Vegard, who are evasive when questioned about it. Contents [hide] 1 Device Overview 1.1 Program Memory 1.2 Data Memory and Registers 1.3 EEPROM 1.4 Program Execution 1.5 Speed 2 Development 3 Features 4 Footnotes 5 See also 6 External Links 6.1 Atmel Official Links 6.2 AVR Forums & Discussion Groups 6.3 Machine Language Development 6.4 C Language Development 6.5 BASIC & Other AVR Languages 6.6 AVR Butterfly Specific 6.7 Other AVR Links [edit] Device Overview The AVR is a Harvard architecture machine with programs and data stored and addressed separately. Flash, EEPROM, and SRAM are all integrated onto a single die, removing the need for external memory (though still available on some devices). [edit] Program Memory Program instructions are stored in semi-permanent Flash memory. Each instruction for the AVR line is either 16 or 32 bits in length. The Flash memory is addressed using 16 bit word sizes. The size of the program memory is indicated in the naming of the device itself. For instance, the ATmega64x line has 64Kbytes of Flash. Almost all AVR devices are self-programmable. [edit] Data Memory and Registers The data address space consists of the register file, I/O registers, and SRAM. The AVRs have thirty-two single-byte registers and are classified as 8-bit RISC devices. The working registers are mapped in as the first thirty-two memory spaces (000016-001F16) followed by the 64 I/O registers (002016-005F16). The actual usable RAM starts after both these sections (address 006016). (Note that the I/O register space may be larger on some more extensive devices, in which case memory mapped I/O registers will occupy a portion of the SRAM.) Even though there are separate addressing schemes and optimized opcodes for register file and I/O register access, all can still be addressed and manipulated as if they were in SRAM. [edit] EEPROM Almost all devices have on-die EEPROM. This is most often used for long-term parameter storage to be retrieved even after cycling the power of the device. [edit] Program Execution Atmel's AVRs have a single level pipeline design. The next machine instruction is fetched as the current one is executing. Most instructions take just one or two clock cycles, making AVRs relatively fast among the eight-bit microcontrollers. The AVR family of processors were designed for the efficient execution of compiled C code. The AVR instruction set is more orthogonal than most eight-bit microcontrollers, however, it is not completely regular: Pointer registers X, Y, and Z have addressing capabilities that are different from each other. Register locations R0 to R15 have different addressing capabilities than register locations R16 to R31. I/O ports 0 to 31 have different addressing capabilities than I/O ports 32 to 63. CLR affects flags, while SER does not, even though they are complementary instructions. CLR set all bits to zero and SER sets them to one. (Note though, that neither CLR nor SER are native instructions. Instead CLR is syntactic sugar for [produces the same machine code as] EOR R,R while SER is syntactic sugar for LDI R,$FF. Math operations such as EOR modify flags while moves/loads/stores/branches such as LDI do not.) [edit] Speed The AVR line can normally support clock speeds from 0-16MHz, with some devices reaching 20MHz. Lower powered operation usually requires a reduced clock speed. All AVRs feature an on-chip oscillator, removing the need for external clocks or resonator circuitry. Because many operations on the AVR are single cycle, the AVR can achieve up to 1MIPS per MHz. [edit] Development AVRs have a large following due to the free and inexpensive development tools available, including reasonably priced development boards and free development software. The AVRs are marketed under various names that share the same basic core but with different peripheral and memory combinations. Some models (notably, the ATmega range) have additional instructions to make arithmetic faster. Compatibility amongst chips is fairly good. See external links for sites relating to AVR development. [edit] Features Current AVRs offer a wide range of features: RISC Core Running Many Single Cycle Instructions Multifunction, Bi-directional I/O Ports with Internal, Configurable Pull-up Resistors Multiple Internal Oscillators Internal, Self-Programmable Instruction Flash Memory up to 256K In-System Programmable using ICSP, JTAG, or High Voltage methods Optional Boot Code Section with Independent Lock Bits for Protection Internal Data EEPROM up to 4KB Internal SRAM up to 8K 8-Bit and 16-Bit Timers PWM Channels & dead time generator Lighting (PWM Specific) Controller models Dedicated IC Compatible Two-Wire Interface (TWI) Synchronous/Asynchronous Serial Peripherals (UART/USART) (As used with RS-232,RS-485, and more) Serial Peripheral Interface (SPI) CAN Controller Support USB Controller Support Proper High-speed hardware & Hub controller with embedded AVR. Also freely available low-speed (HID) software emulation Ethernet Controller Support Universal Serial Interface (USI) for Two or Three-Wire Synchronous Data Transfer Analog Comparators LCD Controller Support 10-Bit A/D Converters, with multiplex of up to 16 channels Brownout Detection Watchdog Timer (WDT) Low-voltage Devices Operating Down to 1.8v Multiple Power-Saving Sleep Modes picoPower Devices Atmel AVR assembler programming language Atmel AVR machine programming language Atmel AVR From Wikipedia, the free encyclopedia (Redirected from Avr) Jump to: navigation, search The AVRs are a family of RISC microcontrollers from Atmel. Their internal architecture was conceived by two students: Alf-Egil Bogen and Vegard Wollan, at the Norwegian Institute of Technology (NTH] and further developed at Atmel Norway, a subsidiary founded by the two architects. Atmel recently released the Atmel AVR32 line of microcontrollers. These are 32-bit RISC devices featuring SIMD and DSP instructions, along with many additional features for audio and video processing, intended to compete with ARM based processors. Note that the use of "AVR" in this article refers to the 8-bit RISC line of Atmel AVR Microcontrollers. The acronym AVR has been reported to stand for Advanced Virtual RISC. It's also rumoured to stand for the company's founders: Alf and Vegard, who are evasive when questioned about it. Contents [hide] 1 Device Overview 1.1 Program Memory 1.2 Data Memory and Registers 1.3 EEPROM 1.4 Program Execution 1.5 Speed 2 Development 3 Features 4 Footnotes 5 See also 6 External Links 6.1 Atmel Official Links 6.2 AVR Forums & Discussion Groups 6.3 Machine Language Development 6.4 C Language Development 6.5 BASIC & Other AVR Languages 6.6 AVR Butterfly Specific 6.7 Other AVR Links [edit] Device Overview The AVR is a Harvard architecture machine with programs and data stored and addressed separately. Flash, EEPROM, and SRAM are all integrated onto a single die, removing the need for external memory (though still available on some devices). [edit] Program Memory Program instructions are stored in semi-permanent Flash memory. Each instruction for the AVR line is either 16 or 32 bits in length. The Flash memory is addressed using 16 bit word sizes. The size of the program memory is indicated in the naming of the device itself. For instance, the ATmega64x line has 64Kbytes of Flash. Almost all AVR devices are self-programmable. [edit] Data Memory and Registers The data address space consists of the register file, I/O registers, and SRAM. The AVRs have thirty-two single-byte registers and are classified as 8-bit RISC devices. The working registers are mapped in as the first thirty-two memory spaces (000016-001F16) followed by the 64 I/O registers (002016-005F16). The actual usable RAM starts after both these sections (address 006016). (Note that the I/O register space may be larger on some more extensive devices, in which case memory mapped I/O registers will occupy a portion of the SRAM.) Even though there are separate addressing schemes and optimized opcodes for register file and I/O register access, all can still be addressed and manipulated as if they were in SRAM. [edit] EEPROM Almost all devices have on-die EEPROM. This is most often used for long-term parameter storage to be retrieved even after cycling the power of the device. [edit] Program Execution Atmel's AVRs have a single level pipeline design. The next machine instruction is fetched as the current one is executing. Most instructions take just one or two clock cycles, making AVRs relatively fast among the eight-bit microcontrollers. The AVR family of processors were designed for the efficient execution of compiled C code. The AVR instruction set is more orthogonal than most eight-bit microcontrollers, however, it is not completely regular: Pointer registers X, Y, and Z have addressing capabilities that are different from each other. Register locations R0 to R15 have different addressing capabilities than register locations R16 to R31. I/O ports 0 to 31 have different addressing capabilities than I/O ports 32 to 63. CLR affects flags, while SER does not, even though they are complementary instructions. CLR set all bits to zero and SER sets them to one. (Note though, that neither CLR nor SER are native instructions. Instead CLR is syntactic sugar for [produces the same machine code as] EOR R,R while SER is syntactic sugar for LDI R,$FF. Math operations such as EOR modify flags while moves/loads/stores/branches such as LDI do not.) [edit] Speed The AVR line can normally support clock speeds from 0-16MHz, with some devices reaching 20MHz. Lower powered operation usually requires a reduced clock speed. All AVRs feature an on-chip oscillator, removing the need for external clocks or resonator circuitry. Because many operations on the AVR are single cycle, the AVR can achieve up to 1MIPS per MHz. [edit] Development AVRs have a large following due to the free and inexpensive development tools available, including reasonably priced development boards and free development software. The AVRs are marketed under various names that share the same basic core but with different peripheral and memory combinations. Some models (notably, the ATmega range) have additional instructions to make arithmetic faster. Compatibility amongst chips is fairly good. See external links for sites relating to AVR development. [edit] Features Current AVRs offer a wide range of features: RISC Core Running Many Single Cycle Instructions Multifunction, Bi-directional I/O Ports with Internal, Configurable Pull-up Resistors Multiple Internal Oscillators Internal, Self-Programmable Instruction Flash Memory up to 256K In-System Programmable using ICSP, JTAG, or High Voltage methods Optional Boot Code Section with Independent Lock Bits for Protection Internal Data EEPROM up to 4KB Internal SRAM up to 8K 8-Bit and 16-Bit Timers PWM Channels & dead time generator Lighting (PWM Specific) Controller models Dedicated IC Compatible Two-Wire Interface (TWI) Synchronous/Asynchronous Serial Peripherals (UART/USART) (As used with RS-232,RS-485, and more) Serial Peripheral Interface (SPI) CAN Controller Support USB Controller Support Proper High-speed hardware & Hub controller with embedded AVR. Also freely available low-speed (HID) software emulation Ethernet Controller Support Universal Serial Interface (USI) for Two or Three-Wire Synchronous Data Transfer Analog Comparators LCD Controller Support 10-Bit A/D Converters, with multiplex of up to 16 channels Brownout Detection Watchdog Timer (WDT) Low-voltage Devices Operating Down to 1.8v Multiple Power-Saving Sleep Modes picoPower Devices Atmel AVR assembler programming language Atmel AVR machine programming language Atmel AVR From Wikipedia, the free encyclopedia (Redirected from Avr) Jump to: navigation, search The AVRs are a family of RISC microcontrollers from Atmel. Their internal architecture was conceived by two students: Alf-Egil Bogen and Vegard Wollan, at the Norwegian Institute of Technology (NTH] and further developed at Atmel Norway, a subsidiary founded by the two architects. Atmel recently released the Atmel AVR32 line of microcontrollers. These are 32-bit RISC devices featuring SIMD and DSP instructions, along with many additional features for audio and video processing, intended to compete with ARM based processors. Note that the use of "AVR" in this article refers to the 8-bit RISC line of Atmel AVR Microcontrollers. The acronym AVR has been reported to stand for Advanced Virtual RISC. It's also rumoured to stand for the company's founders: Alf and Vegard, who are evasive when questioned about it. Contents [hide] 1 Device Overview 1.1 Program Memory 1.2 Data Memory and Registers 1.3 EEPROM 1.4 Program Execution 1.5 Speed 2 Development 3 Features 4 Footnotes 5 See also 6 External Links 6.1 Atmel Official Links 6.2 AVR Forums & Discussion Groups 6.3 Machine Language Development 6.4 C Language Development 6.5 BASIC & Other AVR Languages 6.6 AVR Butterfly Specific 6.7 Other AVR Links [edit] Device Overview The AVR is a Harvard architecture machine with programs and data stored and addressed separately. Flash, EEPROM, and SRAM are all integrated onto a single die, removing the need for external memory (though still available on some devices). [edit] Program Memory Program instructions are stored in semi-permanent Flash memory. Each instruction for the AVR line is either 16 or 32 bits in length. The Flash memory is addressed using 16 bit word sizes. The size of the program memory is indicated in the naming of the device itself. For instance, the ATmega64x line has 64Kbytes of Flash. Almost all AVR devices are self-programmable. [edit] Data Memory and Registers The data address space consists of the register file, I/O registers, and SRAM. The AVRs have thirty-two single-byte registers and are classified as 8-bit RISC devices. The working registers are mapped in as the first thirty-two memory spaces (000016-001F16) followed by the 64 I/O registers (002016-005F16). The actual usable RAM starts after both these sections (address 006016). (Note that the I/O register space may be larger on some more extensive devices, in which case memory mapped I/O registers will occupy a portion of the SRAM.) Even though there are separate addressing schemes and optimized opcodes for register file and I/O register access, all can still be addressed and manipulated as if they were in SRAM. [edit] EEPROM Almost all devices have on-die EEPROM. This is most often used for long-term parameter storage to be retrieved even after cycling the power of the device. [edit] Program Execution Atmel's AVRs have a single level pipeline design. The next machine instruction is fetched as the current one is executing. Most instructions take just one or two clock cycles, making AVRs relatively fast among the eight-bit microcontrollers. The AVR family of processors were designed for the efficient execution of compiled C code. The AVR instruction set is more orthogonal than most eight-bit microcontrollers, however, it is not completely regular: Pointer registers X, Y, and Z have addressing capabilities that are different from each other. Register locations R0 to R15 have different addressing capabilities than register locations R16 to R31. I/O ports 0 to 31 have different addressing capabilities than I/O ports 32 to 63. CLR affects flags, while SER does not, even though they are complementary instructions. CLR set all bits to zero and SER sets them to one. (Note though, that neither CLR nor SER are native instructions. Instead CLR is syntactic sugar for [produces the same machine code as] EOR R,R while SER is syntactic sugar for LDI R,$FF. Math operations such as EOR modify flags while moves/loads/stores/branches such as LDI do not.) [edit] Speed The AVR line can normally support clock speeds from 0-16MHz, with some devices reaching 20MHz. Lower powered operation usually requires a reduced clock speed. All AVRs feature an on-chip oscillator, removing the need for external clocks or resonator circuitry. Because many operations on the AVR are single cycle, the AVR can achieve up to 1MIPS per MHz. [edit] Development AVRs have a large following due to the free and inexpensive development tools available, including reasonably priced development boards and free development software. The AVRs are marketed under various names that share the same basic core but with different peripheral and memory combinations. Some models (notably, the ATmega range) have additional instructions to make arithmetic faster. Compatibility amongst chips is fairly good. See external links for sites relating to AVR development. [edit] Features Current AVRs offer a wide range of features: RISC Core Running Many Single Cycle Instructions Multifunction, Bi-directional I/O Ports with Internal, Configurable Pull-up Resistors Multiple Internal Oscillators Internal, Self-Programmable Instruction Flash Memory up to 256K In-System Programmable using ICSP, JTAG, or High Voltage methods Optional Boot Code Section with Independent Lock Bits for Protection Internal Data EEPROM up to 4KB Internal SRAM up to 8K 8-Bit and 16-Bit Timers PWM Channels & dead time generator Lighting (PWM Specific) Controller models Dedicated IC Compatible Two-Wire Interface (TWI) Synchronous/Asynchronous Serial Peripherals (UART/USART) (As used with RS-232,RS-485, and more) Serial Peripheral Interface (SPI) CAN Controller Support USB Controller Support Proper High-speed hardware & Hub controller with embedded AVR. Also freely available low-speed (HID) software emulation Ethernet Controller Support Universal Serial Interface (USI) for Two or Three-Wire Synchronous Data Transfer Analog Comparators LCD Controller Support 10-Bit A/D Converters, with multiplex of up to 16 channels Brownout Detection Watchdog Timer (WDT) Low-voltage Devices Operating Down to 1.8v Multiple Power-Saving Sleep Modes picoPower Devices Atmel AVR assembler programming language Atmel AVR machine programming language