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    AT89C51 APPLICATION NOTE Search Results

    AT89C51 APPLICATION NOTE Result Highlights (5)

    Part ECAD Model Manufacturer Description Download Buy
    TSL1401CCS-RL2 Rochester Electronics TSL1401 - 128 x 1 Linear Sensor Array with hold. Please note, an MOQ and OM of 250 pcs applies. Visit Rochester Electronics Buy
    C8231A Rochester Electronics LLC Math Coprocessor, 8-Bit, NMOS, CDIP24, DIP-24 Visit Rochester Electronics LLC Buy
    AM79865JC Rochester Electronics LLC Telecom Circuit, Visit Rochester Electronics LLC Buy
    AM79866AJC-G Rochester Electronics LLC SPECIALTY TELECOM CIRCUIT, PQCC20, ROHS COMPLIANT, PLASTIC, LCC-20 Visit Rochester Electronics LLC Buy
    MD8087/R Rochester Electronics LLC Math Coprocessor, CMOS Visit Rochester Electronics LLC Buy

    AT89C51 APPLICATION NOTE Datasheets Context Search

    Catalog Datasheet MFG & Type Document Tags PDF

    DL1414T

    Abstract: 7 segment use at89c51 MICROCONTROLLER AT89C51 11.0592 CRYSTAL used in microcontroller at89c51 max232 with 8051 PROGRAMMER DL1414 moving message display with AT89C51 microcontroller AT89C51 programmer flash programmer circuit for AT89c51 PROCOMM PLUS
    Text: Microcontroller AT89C51 In-Circuit Programming This application note illustrates the in-circuit programmability of the Atmel AT89C51 Flash-based microcontroller. Guidelines for the addition of in-circuit programmability to AT89C51 applications are presented along with an application example


    Original     		AT89C51 AT89C51-XX-5. AT89C51 00000001FF' DL1414T 7 segment use at89c51 MICROCONTROLLER AT89C51 11.0592 CRYSTAL used in microcontroller at89c51 max232 with 8051 PROGRAMMER DL1414 moving message display with AT89C51 microcontroller AT89C51 programmer flash programmer circuit for AT89c51 PROCOMM PLUS PDF

    DL1414T

    Abstract: max232 and 8051 programmer DL1414 7 segment use at89c51 max232 with 8051 PROGRAMMER Microcontroller advantages of AT89C51 moving message display using 8051 11.0592 CRYSTAL used in microcontroller at89c51 11.0592 CRYSTAL used in microcontroller at89c51 p PROCOMM PLUS
    Text: AT89C51 In-Circuit Programming This application note illustrates the in-circuit programmability of the Atmel AT89C51 Flash-based microcontroller. Guidelines for the addition of in-circuit programmability to AT89C51 applications are presented along with an application example and the modifications to


    Original     		AT89C51 AT89C51-XX-5. AT89C51 00000001FF' DL1414T max232 and 8051 programmer DL1414 7 segment use at89c51 max232 with 8051 PROGRAMMER Microcontroller advantages of AT89C51 moving message display using 8051 11.0592 CRYSTAL used in microcontroller at89c51 11.0592 CRYSTAL used in microcontroller at89c51 p PROCOMM PLUS PDF

    C2051

    Abstract: ASSEMBLY LANGUAGE FOR AT89C51 flash programmer circuit for AT89c51 74LS04 pin configuration variable power supply circuit at89 programmer 74LS04 NOT gate pin configuration 74LS04 data chips 74ls04 AT89C51/LV51
    Text: Using a Personal Computer to Program the AT89C51/C52/LV51/LV52/C1051/C2051 Introduction This application note describes a personal computer-based programmer for the AT89C51/C52/LV51/LV52/C1051/C2051 Flash-based Microcontrollers. The programmer supports all flash memory


    Original     		AT89C51/C52/LV51/LV52/C1051/C2051 AT89C51/C52/ LV51/LV52, 74LS541 74LS175 DB25-S C2051 ASSEMBLY LANGUAGE FOR AT89C51 flash programmer circuit for AT89c51 74LS04 pin configuration variable power supply circuit at89 programmer 74LS04 NOT gate pin configuration 74LS04 data chips 74ls04 AT89C51/LV51 PDF

    flash programmer circuit for AT89c51

    Abstract: timer using AT89c51 ASSEMBLY LANGUAGE FOR AT89C51 programmer circuit for AT89c51 AT89C51 microcontroller programming introduction to microcontroller AT89C51 AT89C51 lock bit 8086 assembly language for parallel port atmel AT89C52 PROGRAMMER AT89C51 PROGRAMS
    Text: Microcontroller Using a Personal Computer to Program the AT89C51/C52/LV51/LV52/C1051/C2051 Introduction This application note describes a personal computer-based programmer for the AT89C51/C52/LV51/LV52/C1051/C2051 Flash-based Microcontrollers. The programmer supports all flash memory microcontroller functions, including code read, code


    Original     		AT89C51/C52/LV51/LV52/C1051/C2051 AT89C51/C52/ LV51/LV52, 378-37F 278-27F AT89C flash programmer circuit for AT89c51 timer using AT89c51 ASSEMBLY LANGUAGE FOR AT89C51 programmer circuit for AT89c51 AT89C51 microcontroller programming introduction to microcontroller AT89C51 AT89C51 lock bit 8086 assembly language for parallel port atmel AT89C52 PROGRAMMER AT89C51 PROGRAMS PDF

    flash programmer circuit for AT89c51

    Abstract: ASSEMBLY LANGUAGE FOR AT89C51 AT89C51 microcontroller programming timer using AT89c51 8086 assembly language for parallel port AT89C51 lock bit AT89C51 application note programmer circuit for AT89c51 variable power supply circuit 8086 hex code sheet
    Text: Microcontroller Using a Personal Computer to Program the AT89C51/C52/LV51/LV52/C1051/C2051 Introduction This application note describes a personal computer-based programmer for the AT89C51/C52/LV51/LV52/C1051/C20 51 Flash-based Microcontrollers. The programmer supports all flash memory


    Original     		AT89C51/C52/LV51/LV52/C1051/C2051 AT89C51/C52/LV51/LV52/C1051/C20 AT89C51/C52/ LV51/LV52, 378-37F 27827F AT89C flash programmer circuit for AT89c51 ASSEMBLY LANGUAGE FOR AT89C51 AT89C51 microcontroller programming timer using AT89c51 8086 assembly language for parallel port AT89C51 lock bit AT89C51 application note programmer circuit for AT89c51 variable power supply circuit 8086 hex code sheet PDF

    digital clock using AT89C51

    Abstract: ic at89c51 digital clock programming AT89C51 digital clock using the Atmel AT89C51 at89c52 digital clock program for digital clock AT89C51 atmel 2051 AT89C51 INSTRUCTIONS SET at89c51 digital clock FOR AT89C51
    Text: Designing Boards with Atmel AT89C51, AT89C52, AT89C1051, and AT89C2051 for Writing Flash at In-Circuit Test Recent improvements in chips and testers have made it possible for the tester to begin taking over the role traditionally assigned to the PROM programmer. Instead of having a PROM programmer write nonvolatile memories


    Original     		AT89C51, AT89C52, AT89C1051, AT89C2051 Z18series AT89C AT89C1051/205252 digital clock using AT89C51 ic at89c51 digital clock programming AT89C51 digital clock using the Atmel AT89C51 at89c52 digital clock program for digital clock AT89C51 atmel 2051 AT89C51 INSTRUCTIONS SET at89c51 digital clock FOR AT89C51 PDF

    AT89C51 INSTRUCTIONS SET

    Abstract: AT89C51 INSTRUCTION SET AT89C51 Crystal oscillator 12 MHz MICROCONTROLLER AT89C51 pin diagram program protection mode of AT89c51 flash programmer circuit for AT89c51 AT89C51 PLCC 44 pin 89C51 interfacing AT89C51 PROGRAMMING INTERFACE circuit diagram for AT89C51
    Text: Features • • • • • • • • • • Compatible with MCS-51  Products 4 Kbytes of In-System Reprogrammable Flash Memory Endurance: 1,000 Write/Erase Cycles Fully Static Operation: 0 Hz to 24 MHz Three-Level Program Memory Lock 128 x 8-Bit Internal RAM


    Original     		MCS-51TM 16-Bit AT89C51 AT89C51-24AC AT89C51-24JC AT89C51-24PC AT89C51-24QC AT89C51-24AI AT89C51-24JI AT89C51 INSTRUCTIONS SET AT89C51 INSTRUCTION SET AT89C51 Crystal oscillator 12 MHz MICROCONTROLLER AT89C51 pin diagram program protection mode of AT89c51 flash programmer circuit for AT89c51 AT89C51 PLCC 44 pin 89C51 interfacing AT89C51 PROGRAMMING INTERFACE circuit diagram for AT89C51 PDF

    MICROCONTROLLER AT89C51 pin diagram

    Abstract: AT89C51 Crystal oscillator 12 MHz AT89C51 INSTRUCTIONS SET flash programmer circuit for AT89c51 Microcontroller AT89C51 architecture led interfacing with 89C51 program protection mode of AT89c51 AT89C51 INSTRUCTION SET led interface with AT89C51 AT89C51 PROGRAMMING INTERFACE
    Text: AT89C51 Features • • • • • • • • • • Compatible with MCS-51  Products 4 Kbytes of In-System Reprogrammable Flash Memory Endurance: 1,000 Write/Erase Cycles Fully Static Operation: 0 Hz to 24 MHz Three-Level Program Memory Lock 128 x 8-Bit Internal RAM


    Original     		AT89C51 MCS-51TM 16-Bit AT89C51 -12AC AT89C51-12JC AT89C51-12PC AT89C51-12QC AT89C51-12AA MICROCONTROLLER AT89C51 pin diagram AT89C51 Crystal oscillator 12 MHz AT89C51 INSTRUCTIONS SET flash programmer circuit for AT89c51 Microcontroller AT89C51 architecture led interfacing with 89C51 program protection mode of AT89c51 AT89C51 INSTRUCTION SET led interface with AT89C51 AT89C51 PROGRAMMING INTERFACE PDF

    Application Notes

    Abstract: ELECTRONIC NOTICE BOARD USING AT89S52 circuit Microcontroller AT89S52 microcontroller AT89S51 AT89S52 specification atmel s52 microcontroller AT89S51 PROGRAMMING INTERFACE Microcontroller AT89S52 40 pin Microcontroller AT89s52 datasheet download introduction to microcontroller AT89C52
    Text: Migrating from AT89C51/C52 to AT89S51/S52 Flash Microcontrollers New Features • • • • • • Hardware Watchdog Timer Dual Data Pointer Power-off Flag Interrupt Recovery from Power-down Mode Flexible ISP Programming Byte and Page Modes 42-pin PDIP Package Option for Reduced EMI Emission


    Original     		AT89C51/C52 AT89S51/S52 42-pin AT89S51/S52. AT89LV51/LV52 AT89LS51/LS52. AT89S51/S52 Application Notes ELECTRONIC NOTICE BOARD USING AT89S52 circuit Microcontroller AT89S52 microcontroller AT89S51 AT89S52 specification atmel s52 microcontroller AT89S51 PROGRAMMING INTERFACE Microcontroller AT89S52 40 pin Microcontroller AT89s52 datasheet download introduction to microcontroller AT89C52 PDF

    ic at89c51

    Abstract: Microcontroller AT89C51 architecture AT89C51 microcontroller pin configuration of ic AT89c51 atmel 532 64k at89c51 flash memory Microcontroller advantages of AT89C51 AT29C040 BBS 408-436-4309 AT29C040DA
    Text: Programming Atmel’s Family Of Flash Memories Introduction Atmel offers a diverse family of Flash Memory devices ranging in density from 256 K to 4M-bits. These devices read and program with a single voltage supply. The nominal supply voltage is 5V for the AT29Cxxx, 3.3V for the “low voltage”


    Original     		AT29Cxxx, AT29LVxxx, AT29BVxxx AT89C51 74HCT138 AT89C51 74HCT08 AT29C040 ic at89c51 Microcontroller AT89C51 architecture AT89C51 microcontroller pin configuration of ic AT89c51 atmel 532 64k at89c51 flash memory Microcontroller advantages of AT89C51 AT29C040 BBS 408-436-4309 AT29C040DA PDF

    AT89C51 microcontroller

    Abstract: AT89C51 INSTRUCTION SET BBS 408-436-4309 Microcontroller AT89C51 architecture AT29CXXX AT29C040 AT29LV040 introduction to microcontroller AT89C51 ATmel AT89C51 AT29C040A
    Text: Microcontroller Programming Atmel’s Family Of Flash Memories Flash Introduction Atmel offers a diverse family of Flash Memory devices ranging in density from 256 K to 4 Mbits. These devices read and program with a single voltage supply. The nominal supply voltage is 5 V for the AT29Cxxx, 3.3


    Original     		AT29Cxxx, AT29LVxxx, AT29BVxxx AT89C51 microcontroller AT89C51 INSTRUCTION SET BBS 408-436-4309 Microcontroller AT89C51 architecture AT29CXXX AT29C040 AT29LV040 introduction to microcontroller AT89C51 ATmel AT89C51 AT29C040A PDF

    MICROCONTROLLER AT89C51 pin diagram

    Abstract: Microcontroller - AT89C51 architecture Microcontroller AT89C51 architecture AT89C51 INSTRUCTIONS SET flash programmer circuit for AT89c51 AT89C51 Crystal oscillator 12 MHz atmel 89c51 cc program protection mode of AT89c51 AT89C51 INSTRUCTION SET AT89C51 PROGRAMMING INTERFACE
    Text: Features • Compatible with MCS-51 Products • 4K Bytes of In-System Reprogrammable Flash Memory • • • • • • • • – Endurance: 1,000 Write/Erase Cycles Fully Static Operation: 0 Hz to 24 MHz Three-Level Program Memory Lock 128 x 8-Bit Internal RAM


    Original     		MCS-51TM 16-Bit AT89C51 AT89C51-20PI AT89C51-20QI AT89C51-20AC AT89C51-20JC AT89C51 MICROCONTROLLER AT89C51 pin diagram Microcontroller - AT89C51 architecture Microcontroller AT89C51 architecture AT89C51 INSTRUCTIONS SET flash programmer circuit for AT89c51 AT89C51 Crystal oscillator 12 MHz atmel 89c51 cc program protection mode of AT89c51 AT89C51 INSTRUCTION SET AT89C51 PROGRAMMING INTERFACE PDF

    AT89C51 INSTRUCTIONS SET

    Abstract: program for digital clock AT89C51 digital clock programming AT89C51 digital clock using AT89C51 digital clock using c AT89C51 89c51 c programming codes AT89C51 INSTRUCTION SET MICROCONTROLLER AT89C51 pin diagram at89c51 digital clock digital lock using AT89C51
    Text: Atmel 8051 Microcontroller Family - Product Selection Guide Device 89C1051 89C1051U 89C2051 89C4051 89C51 89C52 89C55 89S8252 89S53 1K 1K 2K 4K 4K 8K 20K 8K 12K ON-CHIP MEMORY Flash Bytes EEPROM (Bytes) 2K SRAM (Bytes) 64 64 128 128 128 256 256 256 256 In-System Programmable (ISP)


    Original     		89C1051 89C1051U 89C2051 89C4051 89C51 89C52 89C55 89S8252 89S53 AT89C51-20PI AT89C51 INSTRUCTIONS SET program for digital clock AT89C51 digital clock programming AT89C51 digital clock using AT89C51 digital clock using c AT89C51 89c51 c programming codes AT89C51 INSTRUCTION SET MICROCONTROLLER AT89C51 pin diagram at89c51 digital clock digital lock using AT89C51 PDF

    Atmel 89C51 microcontroller Datasheet

    Abstract: ATmel 89c51 Atmel 89C51 microcontroller introduction to microcontroller 89C51 A29c040 atmel 89c51 cc AT29 Flash Family ATmel AT89C51 89c51 atmel specification at 89c51 architecture
    Text: Programming Atmel’s AT29 Flash Family Introduction Atmel offers a diverse family of small sector Flash memory devices ranging in density from 256K to 4M bits. These devices read and program with a single voltage supply. The nominal supply voltage is 5V for the AT29CXXX, 3.3V for


    Original     		AT29CXXX, AT29LVXXX, AT29BVXXX 0518B 10/98/xM Atmel 89C51 microcontroller Datasheet ATmel 89c51 Atmel 89C51 microcontroller introduction to microcontroller 89C51 A29c040 atmel 89c51 cc AT29 Flash Family ATmel AT89C51 89c51 atmel specification at 89c51 architecture PDF

    Atmel 89C51 microcontroller pin configuration

    Abstract: Atmel 89C51 microcontroller plcc Datasheet Atmel 89C51 microcontroller Datasheet 89c51 atmel specification AT89C51 PLCC pin details flash programmer circuit for AT89c51 MICROCONTROLLER AT89C51 pin diagram program protection mode of AT89c51 atmel 89c51 cc atmel 89C51
    Text: Features • Compatible with MCS-51 Products • 4K Bytes of In-System Reprogrammable Flash Memory • • • • • • • • – Endurance: 1,000 Write/Erase Cycles Fully Static Operation: 0 Hz to 24 MHz Three-level Program Memory Lock 128 x 8-bit Internal RAM


    Original     		MCS-51TM 16-bit AT89C51 MCS-51 0265G 02/00/xM Atmel 89C51 microcontroller pin configuration Atmel 89C51 microcontroller plcc Datasheet Atmel 89C51 microcontroller Datasheet 89c51 atmel specification AT89C51 PLCC pin details flash programmer circuit for AT89c51 MICROCONTROLLER AT89C51 pin diagram program protection mode of AT89c51 atmel 89c51 cc atmel 89C51 PDF

    AT89C51 INSTRUCTION SET

    Abstract: AT89C51 PROGRAMMING INTERFACE 89c51 atmel programing specification ic at89c51 Flash perom 89C51 At89c51 programming pin diagram of ic 89c51 program data memory 89C51 AT89C51 INSTRUCTIONS SET
    Text: AT89C51 Features • Compatible with MCS-51 1>Products • 4K Bytes of In-Circuit Re-Programmable Flash Memory Endurance: 1000 Write/Erase Cycles Data Retention: 10 Years • Wide Operating Voltage Range: V cc = 2.7V to 6V 8-Bit Microcontroller with 4K Byte


    OCR Scan     		AT89C51 MCS-51 16-Blt AT89C51 91-Zl AT89C51 INSTRUCTION SET AT89C51 PROGRAMMING INTERFACE 89c51 atmel programing specification ic at89c51 Flash perom 89C51 At89c51 programming pin diagram of ic 89c51 program data memory 89C51 AT89C51 INSTRUCTIONS SET PDF

    89c51 can bus

    Abstract: No abstract text available
    Text: AT89C51 Features • Compatible with MCS-51W Products • 4K Bytes of In-Clrcult Re-Programmable Flash Memory Endurance: 1000 Write/Erase Cycles Data Retention: 10 Years • Wide Operating Voltage Range: Vcc = 2.7V to 6V 8-Bit • Fully Static Operation: 0 Hz to 16 MHz


    OCR Scan     		AT89C51 MCS-51W 16-Bit AT89C5 89c51 can bus PDF

    AT89C51 programmer

    Abstract: B9C51 AT89C51 application note programs at89c51 AT89C51 PROGRAMMING INTERFACE In-system Programmer for AT89c51 Microcontroller - AT89C51 used in display bus s
    Text: M icrocontroller Using a Personal Computer to Program the AT89C51 8-Bit M icrocontroller Introduction This note describes a personal computerbased programmer for the AT89C51 Flashbased Microcontroller. The techniques illustrated here can also be used to imple­


    OCR Scan     		AT89C51 AT89C51 AT89C51 programmer B9C51 AT89C51 application note programs at89c51 AT89C51 PROGRAMMING INTERFACE In-system Programmer for AT89c51 Microcontroller - AT89C51 used in display bus s PDF

    atmel 89c51 cc

    Abstract: No abstract text available
    Text: AT89C51 Features • Compatible with MCS-51<1>Products • 4K Bytes of In-Clrcult Re-Programmable Flash Memory Endurance: 1000 Write/Erase Cycles Data Retention: 10 Years • Wide Operating Voltage Range: V c c = 2.7V to 6V • Fully Static Operation: 0 Hz to 16 MHz


    OCR Scan     		AT89C51 16-BIt AT89C5 atmel 89c51 cc PDF

    89c51 hex code

    Abstract: 20C04 ASSEMBLY LANGUAGE FOR AT89C51 29C04
    Text: Flash Programming Atmel’s AT29 Flash Family Introduction Atmel offers a diverse family of small sector Flash memory devices ranging in density from 256K to 4M bits. These de­ vices read and program with a single voltage supply. The nominal supply volt­


    OCR Scan     		AT29CXXX, AT29LVXXX, AT29BVXXX 29C040 0x0400 29C040 AT29C040A AT89C51 89c51 hex code 20C04 ASSEMBLY LANGUAGE FOR AT89C51 29C04 PDF

    MICROCONTROLLER AT89C51 pin diagram

    Abstract: timer using AT89c51 AT89C51 INSTRUCTION SET AT89C51 Crystal oscillator 12 MHz AT89C51-24PI program for at89c51 AT89C51 INSTRUCTIONS SET AT89C51-12PC Microcontroller AT89C51 architecture at 89c51 architecture
    Text: AT89C51 Features • • • • • • • • • • Compatible with MCS-51 Products 4 Kbytes of In-System Reprogrammable Flash Memory Endurance: 1,000 Write/Erase Cycles Fully Static Operation: 0 Hz to 24 MHz Three-Level Program Memory Lock 128 x 8-Bit Internal RAM


    OCR Scan     		AT89C51 MCS-51TM 16-Bit Military/883C MICROCONTROLLER AT89C51 pin diagram timer using AT89c51 AT89C51 INSTRUCTION SET AT89C51 Crystal oscillator 12 MHz AT89C51-24PI program for at89c51 AT89C51 INSTRUCTIONS SET AT89C51-12PC Microcontroller AT89C51 architecture at 89c51 architecture PDF

    AT89C51 INSTRUCTIONS SET

    Abstract: ic at89c51
    Text: Features Compatible with MCS-51 Products 4K Bytes of In-System Reprogrammable Flash Memory - Endurance: 1,000 Write/Erase Cycles Fully Static Operation: 0 Hz to 24 MHz Three-Level Program Memory Lock 1 2 8 x 8 -Bit Interna I RAM 32 Programmable I/O Lines


    OCR Scan     		MCS-51â 16-Bit AT89C51 AT89C51-12PA AT89C51-12JA AT89C51 AT89C51-24AC AT89C51-24JC AT89C51 INSTRUCTIONS SET ic at89c51 PDF

    ic at89c51

    Abstract: MICROCONTROLLER AT89C51 pin diagram AT89C51 INSTRUCTION SET pin configuration of ic AT89c51 ic at89c51 pin diagram pin diagram of ic 89c51 Microcontroller - AT89C51 architecture MC AT89C51 program for at89c51 T89C51
    Text: Features * Compatible with MCS-51 Products * 4K Bytes of In-System Reprogrammable Flash Memory - Endurance: 1,000 Write/Erase Cycles * Fully Static Operation: 0 Hz to 24 MHz * Three-Level Program Memory Lock * 128 x 8-Bit Internal RAM * 32 Programmable I/O Lines


    OCR Scan     		MCS-51TM 16-Bit AT89C51 AT89C51 MCAT89C51-20JC AT89C51-20PC AT89C51-20QC AT89C51-20AI AT89C51-20JI AT89C51-20PI ic at89c51 MICROCONTROLLER AT89C51 pin diagram AT89C51 INSTRUCTION SET pin configuration of ic AT89c51 ic at89c51 pin diagram pin diagram of ic 89c51 Microcontroller - AT89C51 architecture MC AT89C51 program for at89c51 T89C51 PDF

    MICROCONTROLLER AT89C51 pin diagram

    Abstract: AT89C51 INSTRUCTIONS SET 89C51 24 PI timer using AT89c51 AT89C51 Crystal oscillator 12 MHz Microcontroller - AT89C51 architecture AT89C51 AT89C51 24Pi 111 flash programmer circuit for AT89c51 data sheet of at89c51
    Text: AT89C51 Features • • Compatible with MCS-51 Products 4 Kbytes of In-System Reprogrammable Flash Memory Endurance: 1,000 Write/Erase Cycles • Fully Static Operation: 0 Hz to 24 MHz • Three-Level Program Memory Lock • 128 x 8-Bit Internal RAM • 32 Programmable I/O Lines


    OCR Scan     		AT89C51 MCS-51â 16-Bit AT89C51 MICROCONTROLLER AT89C51 pin diagram AT89C51 INSTRUCTIONS SET 89C51 24 PI timer using AT89c51 AT89C51 Crystal oscillator 12 MHz Microcontroller - AT89C51 architecture AT89C51 24Pi 111 flash programmer circuit for AT89c51 data sheet of at89c51 PDF