week12 - Week 12 8051 Memory Interfacing 1 Stored Program...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Week 12 8051 Memory Interfacing
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Stored Program Concept - Again
Background image of page 2
3 Semiconductor Memory Fundamentals ± In the design of all computers, semiconductor memories are used as primary storage for data and code. ± They are connected directly to the CPU and they are the memory that the CPU asks for information (code or data) ± Among the most widely used are RAM and ROM ± Memory Capacity ² The number of bits that a semiconductor memory chip can store is called its chip capacity (bits or bytes)
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 More ± Memory Organization ² Each memory chip contains 2 x locations where x is the number of address pins on the chip ² Each location contains y bits, where y is the number of data pins on the chip ² The entire chip will contain 2 x * y bits ² Ex. Memory organization of 4K x 4: 2 12 = 4096 locations, each location holding 4 bits ² All ROMs have 8 pins for data ± Memory Speed ² To access data, address is presented to the address pins, the read pin is activated, after a certain amount of time, data shows up at the data pins ² Access time
Background image of page 4
5 Examples ± A given memory chip has 12 address pins and 4 data pins ± 2 12 = 4K locations ± 4 bits/location ± 2 KB of memory ± 4Kx4 ± A 512 KB chip has 8 pins for data ± 2 19 = 512K ± 8 bits/location ± 19 address pins ± 512K x 8
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 Memory Types ± ROM is the type of memory that does not lose its contents when power is turned off. It is also called nonvolatile memory. ² PROM (Programmable Memory) • User programmable (one-time programmable) memory • If the information burned into PROM is wrong, it needs to be discarded since internal fuses are blown permanently. • Special equipment needed: ROM burner or ROM programmer ² EPROM (Erasable Programmable ROM) 2,000 times • Allows making changes in the contents of PROM after it is burned • One can program the memory chip and erase it thousands of times • Erasing its contents can take up to 20 minutes; the entire chip is erased • All EPROM chips have a window that is used to shine ultraviolet (UV) radiation to erase its contents • Also referred to as UV-EPROM
Background image of page 6
7 More ± EEPROM (Electrically Erasable ROM) 500,000 times Method of erasure is electrical Moreover, one can select which byte to be erased Cost per bit is much higher than for UV-EPROM ± Flash Memory EPROM First, the process of erasure of the entire contents takes less than a second, or one might say in a flash, hence its name: flash memory When flash memory’s contents are erased, the entire device used to be erased. The erasure can now be done block by block
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8 Flash memory - more Even though flash memories are writeable, like EPROMs they find their widest use in microcomputer systems for storage of firmware Access time 100 ns compared to tens of ms for disk However, flash memory program/erase cycles ~ 100K, 1000 for UV-EPROM, for RAM and disks
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/09/2012 for the course CS cs464 at Bilkent University.

Page1 / 56

week12 - Week 12 8051 Memory Interfacing 1 Stored Program...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online