Nor Flashо?????У?XIP??
?????????ν??о?????У?XIP??????????????????????????????????????CPU???????RAM?????г???????????Nor Flash????г??????????????и?????????????????????????????????
??ν?????в??????????洢??????У?CPU??????????????????????С?Nor Flash????о?????У??????CPU???????Nor flash??????????????????????????????á?
NOR Flash??Nand Flash
????2??flash???????г???????????????????漼????Intel??1988???????????NOR Flash ???????????????????EPROM(Electrically Programmable Read-Only-Memory???????????洢??)??EEPROM(????????洢??Electrically Erasable Programmable Read - Only Memory)?????????档???????1989??????????????NAND Flash ??????????????????????и?????????????????????????????????????????NOR Flash ???????о?????У?XIP ??eXecute In Place??????????ó???????????Flash?????????У????????????????RAM?С?NOR ?????Ч???????1~4MB??С????????к?????Ч?棬???????д???????????????????????NAND?????????????????????????洢????????д??????????????????NAND??????????Flash???????????????????????????NOR??????NAND????Щ????NAND??д??????NOR????
???????????????????????Nor flash????е???????XIP??
XIP??execute in place????о?????У????ó???????????flash?????????????????У????????????????RAM?У?flash???????Nor flash?????????????????????flash????д????????????в??????????????????RAM???
Nand Flash??????IO?????????????е???ж?д???????????????????????????????????????????8???????????д??????????????????????????????????????????CPU??ü???NAND????????????????Nand flash??й????????????????????????Nand flash???????????????????CPU????????????????s3c2440???????NandFlash??????????????????????NandFlash??4k????????0??SRAM?С????CPU??????????????????????????????NandFlash????????????Nand Flash????????????????????????
Nor Flash??????????У?Nand Flash????????????????
Nor Flash ??Nand Flash????????????
?????????????????????????????????????flash?????????????Nand Flash??CPU?????Nand Flash?ж???????????????????RAM?м???????????????????????MMU????????????Nand flash?????????????????????????Nand Flash??????????????????????????????????????????????RAM?У??????д?????????д??????
??????????????Nor Flash?????????????CPU???????????????????Nor flash????????????????Nor Flash?????????????????????????????У????????????Nand flash??Nor flash?????????CPU????????????????????????
??????? ???Nor Flash???????XIP????Nand flash????????
????????????????д??????з????
??1??????????????????????????????д?????????洢????Flash??ROM????????RAM?????С?
??2?????????????????????RAM?У??????????RAM?е?????е???/?????????????????λ??????е?????????RAM?л???????λ????????????????????RAM?С?
??3??XIP????????????????????????RAM?????????????????洢λ????У?RAM?????????????仯????????????????????
???????XIP????
??????????洢????Flash???????????RAM???????XIP??????????????????Nor flash??rom?????????????100ns??????????XIP????Nand flash???????????????????????????????us????????????????XIP????????Nand flash??д????Nor???????????洢??????????
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- NOR flash?????????????У??????????????CPU??????????е????CPU??????????????Nor flash????????????????CPU??У??м??????????????????
- NAND flash??????????nand flash?е???????????????IO???????cpu?????????????????????????????????????????????????ɡ??????????????SRAM????
????????
о??????????????о????????????洢??????????????о?????????????о???洢????????????????????飩?????????????У?????Flash???????????λ?????bitconvert??????Flash??λ????????bitλ????????????????NAND???????????NorFlash?????????????Flash?洢?????????????????????????NandFlash??????????EDC/ECC??У?????? ??
???????????????????????????????XIP??????????????д?????
????νXIP,????CODE????FLASH?????????. NANDFLASH?????????XIP,?????????????XIP??
????CODE????????????,????????CODE????????,?????.
?????Щ????????????,NOR FLASH????????????,????????????,?????????XIP.
??????NAND FLASH, ??????????BLOCK 0????,??????鲢?????,???????????????,???????г????????,????CODE??????????????????С?
???????ж?????????,??????????CODE????????ECCУ??,?????CODE???????????.???????????XIP. ???????????,???????????????
????Simon ?????????2019-06-26
