REX:flash
Compatible flash chip for REX
The flash chip in the pre-loaded DigiKey cart may be out of stock because it is becoming obsolete.
The exact part in the cart is just one of several equivalent compatible parts that could be used in it's place.
There are several properties that you have to verify in order to find another part that is compatible.
You may have to search ebay or other suppliers for these parts.
The specs you need are:
- parallel flash memory
- 5 volt
- single power supply / single voltage (same 5v used for reading and programming)
- 8 Mbit (1Mx8/512Kx16)
- boot sector
- bottom boot
- TSOP48
- 90ns or faster
The generic part number series is "29F800", with different extra characters added depending on manufacturer.
To search for a compatible flash chip, follow this:
1) Start by searching for "29F800" on any supplier site like DigiKey, Mouser, ebay, Verical, etc, or just google.
- All the parts turned up from that search should be:
- flash memory
- single power supply
- 5v
- 8Mbit x8/x16
- boot sector / boot block
- There is no consistent way to search for, or eliminate, the remaining specs by part number, because each manufacturer specifies these properties differently in their part numbers.
- For each potential part...
2) Search for the datasheet for that part number. Find the legend that shows how to decipher the part number. Usually it's towards the end of the document. Using the part number legend...
3) Verify the part is a TSOP48 package, standard pinout. (If there is no separate "reversed pinout" option, then the pinout is standard.)
4) Verify the boot block is "bottom boot".
5) Any speed 90ns or faster is ok, but the slower the better. (Old computers are crude and have a lot of noise on the bus, and fast parts can be fast enough to misinterpret some noise as data, while the noise is too high frequency to register as a valid pulse for a slower part. So slower is actually better than faster in this case.)
6) Any temperature range is fine. It doesn't hurt to get the more expensive industrial, automotive, or military temperature ranges, but the cheaper more common commercial range is fine.
7) Other possible options like burn-in, packaging, rohs, etc you can ignore.
Some examples of compatible parts
Examples:
Alliance AS29CF800B-**T** AS29CF800B-55TIN Macronix MX29F800*BT*-*** MX29F800CBTI-70G MX29F800BTC-70 Micron / Alliance (Originally a Micron part, discontinued, now Alliance makes a clone.) M29F800FB**N** M29F800FB5AN6E2 AMD AM29F800BB-##E* AM29F800BB-70EC AM29F800BB-70EI AM29F800BB-70EK AM29F800BB-90EF AM29F800BB-55EC STMicroelectronics M29F800*B##N# M29F800AB90N1 M29F800DB70N6 Fuji MBM29F800BA-##PFTN MBM29F800BA-70PFTN Motorola *29F800*5*BT## M29F800A5KBT80
Part number legends for a few manufacturers
Alliance
AS 29CF 800 B - 55 T I N
| | | | | | +- rohs
| | | | | +- temperature
| | | | +- tsop
| | | +- speed
| | +- bottom boot
| +- 8M
|
+- parallel flash, 5v
--------------------------------------------------------------------------
AMD
AM 29F 800B B - 70 E K
| | | | | +- temperature
| | | | +- tsop
| | | +- speed
| | +- bottom boot
| +- 8M, boot block
+- parallel flash, 5v
--------------------------------------------------------------------------
Macronix
MX 29F 800 C B T I - 70 G
| | | | | | | +- rohs
| | | | | | +- speed
| | | | | +- temperature
| | | | +- tsop
| | | +- bottom boot
| | +- revision
| +- 8M
+- parallel flash, 5v
--------------------------------------------------------------------------
STMicroelectronics
M 29 F 800D B 55 N 6
| | | | | | +- temperature
| | | | | +- tsop
| | | | +- speed
| | | +- bottom boot
| | +- 800A, 800D: 8M, x8/x16, Boot Block
| +- 5v
+- flash
--------------------------------------------------------------------------
Fuji
MBM 29F 800 B A - 70 PFTN
| | | | | +- PFTN = tsop48, standard pinout
| | | | +- speed
| | | +- revision
| | +- bottom boot
| +- 8M
+- parallel flash, 5v
--------------------------------------------------------------------------
Motorola
M 29F 800 A 5 K B T 80
| | | | | | | | +- speed
| | | | | | | +- tsop
| | | | | | +- bottom boot
| | | | | +- temperature
| | | | +- 5v
| | | +- revision
| | +- 8M
| +- parallel flash
+- status M: motorola qualified
example links
- Pick any version of the chip which matches this pattern:
- AM29F800BB-##E*
- Where:
- ## = Speed: 90 or faster (90 or less)
- E = Package: Must be "E", which is TSOP
- * = Temperature range code: Any
- Examples:
- AM29F800BB-70EK
- AM29F800BB-90EF (except, that particular entry has a minimum order quantity of 98, at $6 per chip. So you can't use this link to buy 3 chips, but it shows how to identify a correct part. Otherwise this part matches because: The datasheet for AM29F800BB shows that the 2nd "B" in "29F800BB" means bottom boot, and the "E" in "-90EF" means TSOP48)