Post by thread:[EE]: Flash endurance

I need 512k x 8 storage space which can be done with a single 29C040A Flash. The quoted figure for Flash is > 10,000 write cycles. I "might" have a look at battery backed-up SRAM, I've a few 8M TSOPs, but truly NV is preferable Does the endurance refer to the number of times a bit changes state or the number of times that bit is written to, whether it changes state or stays the same ? As the PIC's Flash memory can be re-programmed ~1,000 times that makes me wonder. Could that be Microchip's definition of > 10,000, ie 14 bits x 1,000 ? If, (as I think because the 29C040A data doesn't say otherwise), it means each sector can be over-written 10,000 times however the contents change, then I'm OK, else I'll go with 8 x 24C512 EEPROM (> 10,000,000 writes but more board and 3x the price) -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On 5 Aug 2002 at 16:49, Jinx wrote: > Does the endurance refer to the number of times a bit changes > state or the number of times that bit is written to, whether it > changes state or stays the same ? I think with Flash you can't re-write anything, you need to erase it first. Some let you erase just a single byte, others a page, still others the whole chip. Does that make it easier or harder? -- Brent Brown, Electronic Design Solutions 16 English Street, Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/txt: 025 334 069 eMail: spam_OUTbrent.brownTakeThisOuTclear.net.nz -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> I think with Flash you can't re-write anything, you need to erase > it first. Some let you erase just a single byte, others a page, still > others the whole chip. Does that make it easier or harder? The 29C040A does an automatic erase before write, so that's covered. It also has a small sector size of 256 bytes (2048 of them), which is about all you can load into an F877. As far as I can see, the smallest sector size in a "large" Flash memory is 64 bytes. It's a read-modify-write operation - you have to load the sector into the PIC, modify it and then write it back as a whole sector (AFAIK). Other Flash chips have very large sectors that need a separate SRAM to copy them into, and the erasure of those large sectors when writing back can take some time (many seconds), whereas small sectors can be modified in a few 10's of ms -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

My guess then is that the endurance is the number of times a location can undergo the read/write procedure, I would count 1 for each read/modify/write even though there are 2 steps in the process. Worst case you will be out by a factor of 2? Have looked at some Samsung SmartMedia chips recently and they say less than 0.1% failure in 1 million program/erase cycles. I think the idea is it's anyones guess when they actually fail and you need to take this into account with bad block mangement. -- Brent Brown, Electronic Design Solutions 16 English Street, Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/txt: 025 334 069 eMail: .....brent.brownKILLspam@spam@clear.net.nz -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> The 29C040A does an automatic erase before write, so that's > covered. It also has a small sector size of 256 bytes (2048 of > them), which is about all you can load into an F877. As far as I > can see, the smallest sector size in a "large" Flash memory is > 64 bytes. It's a read-modify-write operation - you have to load the > sector into the PIC, modify it and then write it back as a whole > sector (AFAIK). Other Flash chips have very large sectors that > need a separate SRAM to copy them into, and the erasure of > those large sectors when writing back can take some time (many > seconds), whereas small sectors can be modified in a few 10's > of ms I guess you have been reading too much of the ..A or 18F... Datasheets. The 16f87* (without A!) can write a single instruction (14 bits) at a time. Wouter van Ooijen -- ------------------------------------ http://www.voti.nl PICmicro chips, programmers, consulting -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

>16f87* can write a single instruction (14 bits) at a time. Hi, yes it can. I was speculating on why PIC flash appears to have 1/10th of the write cycle endurance of other flash (which is called RAM, rather than "program memory") -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

I would consider FRAM (ferroelectric ram) devices in lieu of FLASH. Bob Ammerman RAm Systems ----- Original Message ----- From: "Brent Brown" <brent.brownKILLspamCLEAR.NET.NZ> To: <.....PICLISTKILLspam.....MITVMA.MIT.EDU> Sent: Monday, August 05, 2002 2:08 AM Subject: Re: [EE]: Flash endurance {Quote hidden}> My guess then is that the endurance is the number of times a location > can undergo the read/write procedure, I would count 1 for each > read/modify/write even though there are 2 steps in the process. Worst > case you will be out by a factor of 2? > > Have looked at some Samsung SmartMedia chips recently and they say > less than 0.1% failure in 1 million program/erase cycles. I think the > idea is it's anyones guess when they actually fail and you need to > take this into account with bad block mangement. > > -- > Brent Brown, Electronic Design Solutions > 16 English Street, Hamilton, New Zealand > Ph/fax: +64 7 849 0069 > Mobile/txt: 025 334 069 > eMail: EraseMEbrent.brownspam_OUTTakeThisOuTclear.net.nz > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

>FRAM (ferroelectric ram) devices in lieu of FLASH http://www.ramtron.com/aboutfram/aboutfram.htm Might do for a future product but for the present I can't see one bigger than 256k, which is a long way short of the 4M I need. I have no idea who the local supplier would be to ask - what's the price like ? -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On 6 Aug 2002 at 1:41, Jinx wrote: > >FRAM (ferroelectric ram) devices in lieu of FLASH > > http://www.ramtron.com/aboutfram/aboutfram.htm > > Might do for a future product but for the present I can't see one > bigger than 256k, which is a long way short of the 4M I need. I have > no idea who the local supplier would be to ask - what's the price like I have some sample FM24CL64 and FM25CL64's from this place: Non Volatile Technologies http://www.nvtech.com.au Ph: 0061 2 9540 9027 Fax: 0061 2 9540 9017 23 Avenel Road Gymea Bay NSW 2227 Australia Customer gave me the samples so I don't know the price, much less than NZ$10ea anyway. -- Brent Brown, Electronic Design Solutions 16 English Street, Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/txt: 025 334 069 eMail: brent.brownspam_OUTclear.net.nz -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> I have some sample FM24CL64 and FM25CL64's from this place: > > Non Volatile Technologies > http://www.nvtech.com.au > Ph: 0061 2 9540 9027 > Fax: 0061 2 9540 9017 > 23 Avenel Road > Gymea Bay NSW > 2227 Australia Cheers, I'll look into it. From my Google search it appears many of the large manufacturers have either got Ramtron licences or are designing their own. I expect FRAM will be as common and cheap as SRAM shortly -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

>I need 512k x 8 storage space which can be done with a single >29C040A Flash. The quoted figure for Flash is > 10,000 write >cycles. I "might" have a look at battery backed-up SRAM, I've a >few 8M TSOPs, but truly NV is preferable You may like to look at the maxim/Dallas DS1251 which is a 512k byte battery backed SRAM with phantom clock. Appreciate you don't need the clock, and it does not take address space. Comes in 32 pin dip or 34 pin powercap formats. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> You may like to look at the maxim/Dallas DS1251 which > is a 512k byte battery backed SRAM with phantom clock Nice idea Alan but............ I'd priced the DS1245 (1M) previously at $51 inc tax so I had an inkling of what to expect in the way of cost. As of this morning the DS1251 at Arrow is $271 inc tax, MOQ 10 pieces, 5 month lead time. With all due respect, I'll pass on that thank you -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

>Nice idea Alan but............ Yeah, OK, I can see that those prices would make one gasp a bit. Oh well it might be back the 64256 chips then :) -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.