A Find: Cheap and fast EEPROMs, also large and fast EEPROMs
Peter Jakacki
Posts: 10,193
I just went to check my shopping cart at Digikey and they were pretty much out of stock of the common 24LC256 EEPROMs that I use so I had a good look around. It turns out that there is heaps of stock of a faster 1MHz part at 75% of the cost. So I changed my order of course. The part is a FT24C256A-USR-T and costs 50cents in 250 quantities and even better in 1K quantities.They have about 15,000 in stock at present and although it's described as an "SOP" part it is the standard 0.150" width SOIC. All the specs are same or better than the regular parts.
This also revitalized my interest in fast EEPROM and higher capacities which brings me to the next device, the M24M01-RMN6TP, a 128kbyte fast EEPROM with additional 256 byte lockable ID page and 4 million cycle minimum endurance. In terms of bytes per buck it is on par with the cheap FT part and cost $2.10 at 250 off.
So I ordered 25 of these to play with as I figure that my Tachyon Forth could make good use of this extra capacity and speed without introducing extra chips. Source code can be edited, saved, and loaded in this small space as well as having the extra memory for all those help functions where each Forth word's stack comment and description can be referenced.
Now this brings me to mention something: What's happened with Holly's marvellous finds that we used to love picking through?
This also revitalized my interest in fast EEPROM and higher capacities which brings me to the next device, the M24M01-RMN6TP, a 128kbyte fast EEPROM with additional 256 byte lockable ID page and 4 million cycle minimum endurance. In terms of bytes per buck it is on par with the cheap FT part and cost $2.10 at 250 off.
So I ordered 25 of these to play with as I figure that my Tachyon Forth could make good use of this extra capacity and speed without introducing extra chips. Source code can be edited, saved, and loaded in this small space as well as having the extra memory for all those help functions where each Forth word's stack comment and description can be referenced.
Now this brings me to mention something: What's happened with Holly's marvellous finds that we used to love picking through?
Comments
http://www.digikey.com/product-detail/en/FT24C256A-UTR-T/1219-1116-1-ND/3516068
With EEPROM, there is a price premium for the Endurance and fine-Write.
If you just need storage, try dropping W25Q into Digikey;s engine.
- now you will find that 8M Bit of Serial memory, is just 36c/250+ - ie even less than your 256kb device
The very low cost of the W25Q parts, raises the question of when will it make sense to use a small bridge uC, to let the Prop 1 boot from W25Q parts ? - Such a bridge chip could either look like a PC serial host, or a i2c slave chip. Which would be fastest ?
I use the SPI parts too but these cheaper and faster parts are drop-in compatible which is why I mentioned them but they just don't compare in price and speed to the SPI parts. However, the SPI parts are Flash block devices and not as friendly in that respect whereas the EEPROMs can just rewrite a single byte.
You bring up a good idea though, about pairing an SPI device with a small bridge micro, however the problem would not only be physical size but also ICP of the part in the first place (forget headers, yuck). I use various kinds of small micros and the Silabs parts are certainly fast enough and ICP with just one dedicated pin and the other is the I2C data line anyway. These could be initially programmed with a simple load to Prop RAM which would burn the chip. The best part I could find was the C8051F527A-IM in a 10-pin DFN pack for around $1.40 in 100s. This teamed with the SPI memory could also emulate much faster I2C speeds as well or my hybrid I2C/SPI protocol where the initial access is done in I2C after which the data can be read or written at SPI speeds without regard to the protocol until a start or stop condition at normal I2C speeds.
There is also a C8051T606-GT in MSOP10, at 73c/100+, which could be used when code is stable.
Also new, with no price indication yet is this new MSOP10 device - [ wider Vcc, Flash, and adds ADC over the T606]
http://www.syncmos.com.tw/products_file/ISSFD-M067_A_SM39R08A5-DDatasheet%28EN%29.pdf
Hopefully, it will be cheaper or similar in price to the similar ST part : STM8S003F3U6TR QFN20 ( ~44c/100+)
I've been looking at the STM8 parts and the smallest part they have is in a 20-UFQFN for $1.54 @100. I will keep my eye open for the SyncMOS parts but where can you buy SyncMOS?
Avnet list the STM8S003F3U6TR at 44c/100 and Newark show 74c 100+ (45c/2500).
I've asked about samples/pgmrs for SM39R08A5 - no reply yet.