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:

Macronix
MX29F800*BT*-***
  MX29F800CBTI-70G‎
  MX29F800BTC-70

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

--------------------------------------------------------------------------

AMD
AM 29F 800B B - 70 E K
   |   |    |   |  | +- temperature
   |   |    |   |  +- tsop48
   |   |    |   +- speed
   |   |    +- bottom boot
   |   +- 8M, x8/x16, boot block
   +- flash, 5v

--------------------------------------------------------------------------

Macronix

MX 29 F 800 C B T I - 70 G
   |  | |   | | | |   |  +- rohs (may be absent)
   |  | |   | | | |   +- speed
   |  | |   | | | +- temperature
   |  | |   | | +- tsop
   |  | |   | +- bottom boot
   |  | |   +- revision
   |  | +- 8M, x8/x16, Boot Sector
   |  +- 5v
   +- flash, single ps

--------------------------------------------------------------------------

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 29 F 800 B A - 70 PFTN
             |        + PFTN = tsop48, standard pinout
             +- bottom boot

--------------------------------------------------------------------------

Motorola

M 29F 800 A 5 K B T 80
| |   |   | | | | | +- speed
| |   |   | | | | +- tsop
| |   |   | | | +- bottom boot block
| |   |   | | +- temperature
| |   |   | +- voltage
| |   |   +- die revision
| |   +- density/config 8M x8/x16
| +- 29F = Single power supply
+- status M: motorola qualified

example links

• AM29F800BB from Verical

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. This part is good because: The datasheet for AM29F800BB shows that the 2nd "B" in "29F800BB" means bottom boot, and the "E" in "-90EF" means TSOP48, and "90" is a good speed, and the "F" temperature range doesn't matter to us.)