Anyone using FLASH instead of EEPROM?

enso · Post by **enso** » Wed Mar 31, 2021 10:38 pm

I was looking at the specs for SST39SF010, and it looked pretty good: 128K x 8 at 55ns or 70ns, and under $2.00! My cheapo programmer claims to support them...

Has anyone here tried to use one of these? cbmgeeks, I just saw you mention the same chip a couple of years back. Any luck?

Michael · Post by **Michael** » Thu Apr 01, 2021 12:12 am

I'm ready to start using them.

I designed an Arduino shield specifically for programming 28C256 EEPROMs and the SST39SF series 128K, 256K, and 512K Flash ROM chips. The Flash ROM chips are very nice and while you can only program them a byte-at-a-time, they only need 14 to 20-usecs to program each byte. I can program each byte within the ~86-usec interval between incoming 115200 baud serial characters.

I'm also thinking about a Programmer / ROM Emulator design which could use either a RAM chip or a Flash ROM chip when in 'Emulator' mode.

Regards...

ojanhk · Post by **ojanhk** » Thu Apr 01, 2021 6:43 am

enso wrote:

I was looking at the specs for SST39SF010, and it looked pretty good: 128K x 8 at 55ns or 70ns, and under $2.00! My cheapo programmer claims to support them...

Has anyone here tried to use one of these? cbmgeeks, I just saw you mention the same chip a couple of years back. Any luck?

Hi,
Yes, I'm using it a lot, programming it through a TL866II and it works perfectly.
I use it for home made 6502 computer but also as a replacement ROM chip for multiple Atari ST.

Just one point though, I only use it as a ROM, programming through the TL866 only.

jds · Post by **jds** » Thu Apr 01, 2021 9:13 am

I’ve got one in the ZIF socket of my new Forth computer, and have managed to program it successfully in place. By that I mean it is sitting on the 6502 bus like any other chip. To program it you need to write to some special locations with a sequence of values, so it’s not a fast process, but it’s relatively easy and worked the first time I tried it. It’s a huge amount of storage, mine is banked as 16 8k banks, but the Forth has some predefined bank instructions so it’s almost as easy as reading and writing to any other location.

Martin A · Post by **Martin A** » Thu Apr 01, 2021 9:38 am

I use the SST chips all the time because they're so reasonably priced. About the only time I use an 27xx Eprom or 28xx Eeprom is when I'm constrained by space or an existing board to use a 28 pin device. They also seem to have a bit of headroom to push the spec, though of course that's not guaranteed. I've used the 70ns DIP part with the W65C02 at 16mhz and one of the 45ns PLCC parts with oveclocked Z80 at 40mhz.

plasmo · Post by **plasmo** » Thu Apr 01, 2021 10:31 am

Martin A wrote:

. I've used the 70ns DIP part with the W65C02 at 16mhz and one of the 45ns PLCC parts with oveclocked Z80 at 40mhz.

Z80 overclocked to 40 MHz? Impressive! The highest I'm able to achieve is 33mhz with a Z80 in PLCC package and 2"x3" pc board.
Bill

Guus Assmann · Post by **Guus Assmann** » Thu Apr 01, 2021 8:05 pm

I have used this chip in the MegaSpeedy 1050 design for the Atari 8 bit diskdrive, model 1050.
It is reprogrammed in the board, in case another drive emulation is wanted.
The software is not written by me.
Also the XC95144 is also programmed by the software designer.
But the hardware is mainly my design.
I chose the part for the low price and more than big enough size. This design used the PLCC version.
Any OS for the drive is max 8K so plenty of room.

I used the DIL version in an Atari ST and TT.
There it's enough to hold 4 OS-es and it can also be reprogrammed inside the computer.

BR/
Guus