SECTION II-4: PIC micro-controller data RAM and EEPROM

SECTION  II-4: PIC micro-controller data RAM and EEPROM

ROM is used to store program code. The RAM space is for data storage. The PIC18 has a maximum of 4096 bytes (4K) of data RAM space. Not all of the family members come with that much RAM. The data RAM size for the PIC18 varies from 256 bytes to 4096 bytes. The data RAM space has two components: General-purpose RAM (GPR) and Special Function registers (SFRs). SFRs are fixed and every micro-controller must have them. It is the GPR's size that varies from chip to chip. The Microchip website gives only the GPR size. The RAM GPR space is used for read/write scratch pad and data manipulation and is divided into banks of 256 bytes each. The GPR size given for the PIC18 is always a multiple of 256 bytes. In some of the PIC family members, we also have a small amount of EEPROM to store critical data that does not need to be changes very often. Every PIC18 muct have some data RAM for scratch pad, the EEPROM is optional, not all versions of the PIC18 some with EEPROM. EEPROM is used mainly for storage of critical data.

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