Write ability and storage permanence of memories:
Write ability is the manner and speed at which memory can be written.
Storage permanence is the ability of memory to hold stored bits after they are written.
Write ability:
Ranges of write ability:
High end
The processor writes to memory simply and quickly. E.g. RAM
Middle range
The processor writes to memory, but slower. E.g. Flash, EEPROM (Electrically Erasable and Programmable Read Only Memory)
Lower range
Special equipment,"programmer" must be used to write memory. E.g. EPROM, OTP ROM (One Time Programmable Read Only Memory)
Low end
Bits stored only during fabrication. E.g. Mask-programmed ROM
In system programmable memory
Can be written to by a processor in the embedded system using the memory.
Memories in high end and middle range of write ability.
Storage permanence:
It is the ability to hold the stored bits.
The range of storage permanence
High end
Essentially never losses bits. E.g. mask-programmed ROM
Middle range
Hold bits days, months, or years after memory's power source turned off. E.g. NVRAM
Lower range
Holds bits as long as power supplied to memory. E.g. SRAM
Low end
Begins to lose bits almost immediately after written. E.g. DRAM
Nonvolatile memory
Holds bits after power is no longer supplied.
High end and middle range of storage permanence.