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 to meet are:

parallel flash memory

5v

single power supply (same voltage 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.

That gets you all parts that meet most of the specs, and now you still need to check for a few more specs more manually.

All parts that have "29F800" in the part number should be:

flash memory

single power supply

5v

8Mbit x8/x16

boot sector / boot block

There is no consistent way to search or for eliminate the remaining specs by part number pattern, because each manufacturer specifies these properties differently in their part numbers.

2: For each potential part, you may have to search the exact part number on-line to find a datasheet for that part, to decipher the part number to find out if it matches all the specs.

• Ignore all parts that are not TSOP48 package. On most sites you can tell this at a glance from the picture without needing the datasheet.

• You need the datasheet to make sure the part is "bottom boot", or "top boot", or other like "flash file", or no boot

Most parts are either "bottom boot" or "top boot", and we need "bottom boot"

Search for the datasheet for the potential part, usually go to the end or near the end of the datasheet , and find the page that shows the legend for how the part number is constructed, and use that to decipher the part number you are looking at.

3: Any speed 90ns or faster is ok, but the slower the better, 90 is already much faster than the Model 100 operates at anyway, and generally old computers are crude devices and the digital signals on the bus are a bit noisy by todays standards, and it's possible for very fast chips to see the noise as data, because they actually operate that fast, while a slower chip is "blind" to high frequency noise. The Model 100 actually only needs abbout 200ns for it's ram and rom, but the specs from Steven Adolph for REX say 90ns. Maybe slower is actually ok, or maybe the CPLD on the rex itself needs the flash to be that fast even if the Model 100 doesn't. Most parts are 70ns and there is no reason not to just get that.

4: Any temperature range is fine. But you may opt for the extended temperature ranges if you want. You can ignore this part of the part number, or if you have a range of choices available, get whatever you want. But the standard, most common, cheapest "commercial" range (usually 0c to 70c) is fine.

5: Other possible options like burn-in, packaging, etc you can ignore.

Some examples of compatible parts

Examples:

<pre> 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 </pre>

Part number legends for a few manufacturers

<pre> -------------------------------------------------------------------------- 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 </pre>

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• Parts, excluding the flash

This cart is pre-loaded with quantities to build 3 REX boards.

• 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. The datasheet for AM29F800BB shows that the 2nd B in "29F80BB" 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.)