After lot of reading i found some valuable information and now i want to share it with the microcontroller projects community. PIC18 microcontrollers implement a 21-bit program counter, which is capable of addressing a 2-Mbyte program memory space. Any microcontroller can use this chip to store data. By default, this is the most common and used type of memory. Flash memory is the memory that normally stores data that does not change. The data memory contains Special Function Registers (SFRs) and General Purpose Registers (GPRs). In the past, erase commands erased the entire memory chip - therefore to keep a working copy of that data during run-time, an application required additional memory. Embedded C. 21. Figure  shows the data memory organization for the PIC18F2420/2520/4420/4520 devices. Description The AT89C5132 is a mass storage device controlling data exchange between various Flash modules, HDD and CD-ROM. Data flash memory 8-KB data flash memory. To prevent the PC from becoming misaligned with word instructions, the Least Significant bit of PCL is fixed to a value of ‘0’. The machine code for a PIC18 instruction has only 8 bits for a data memory address which needs 12 bits. The architecture of a microcontroller may require that variables and constants be stored in different types of memory. The AT89C5132 includes 64K Bytes of Flash Memory and allows In-System Programming through an embedded 4K Bytes of Boot Flash Memory.The AT89C5132 include 2304 Bytes of RAM Memory.. Data that needs to be kept and does not change frequently can be stored in this area. Additional detailed information on the operation of the Flash program memory is provided in Section 6.0 “Flash Program Memory”. The upper byte is called PCU. By default, this is the most common and used type of memory. Fig. This is due to the way that EEPROM itself is constructed, a function of electro-chemistry. Some EEPROM memory can have write operations as high as the hundreds of thousands and These are SRAM, FLASH, and EEPROM memories. Code flash memory Maximum 256-KB code flash memory. Any read of an unimplemented location will read as ‘0’s. storage or the location of data is in that memory area. The entire data memory may be accessed by Direct, Indirect or Indexed Addressing modes. and arithmetic look-up tables in this region directly frees up valuable SRAM space. repetitively in a program should be stored in another type of memory. The PIC18F2420 and PIC18F4420 each have 16Kbytes of Flash memory and can store up to 8,192 single-word instructions. This is a waste of 30 bytes of SRAM unless the string is intended for alteration See the datasheet Use of Flash Memory in Microcontrollers Flash Memory is a type of non-volatile memory that, unlike RAM, retains its data for an extended period, even if the microcontroller is turned off. When the differences between microprocessor and microcontroller are mentioned in the previous tutorial, the main difference can be stated as on-chip memory i.e. The program memory map for PIC18F2420/2520/ 4420/4520 devices is shown in Figure, Data register map  - with 12bit address bus  000-FFF, Half of bank 0 and half of bank 15 form a virtual bank that is accessible no matter which bank is selected, Bank address (4-bit) + Instruction (8-bit), Indirect using File Select Registers (FSR), FSR contains the address of the data register, Access Bank using General Purpose Registers (GPR), Created, Edited and Notes by Prof. Sujit Wagh, SKNCOE, Pune. Flash LMU (LMURAM, TRAM, EMEM) TriCore 1.6P PMI DMI Overlay FPU TriCore … The code that is written by the user to perform a specific task by the MCU is stored in the FPM (Flash Program Memory) of the MCU. for data (SRAM), program (FLASH), and EEPROM memoriy. Data EEPROM is discussed separately in Section 7.0 “Data EEPROM Memory”. 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