Flash Memory Help

[Travis_Weesner]

The following chip has gone obsolete AM29F040B-70JF-ND and the recommended replacement is the SST39 series from MicrochipTechnology. However, the original booted automatically and the replacement needs to be booted manually. I don’t know enough about these FLASH ICs, is there anybody out there with some experience with this that might have some input?

[Travis_Weesner]

Potential solution provided per below:

@David_1528

Has the customer already inserted the SST39 in circuit in place of the AM29F040B?

I have no direct experience with either, but after a first pass through each datasheet, although the architectures are a bit different between the two, neither has a boot block section, which is typically used by the accompanying MCU/MPU during boot-up. Regardless, I believe that the boot function is controlled by the MPU rather than the flash chip itself, so that should not be dependent on the flash chip. The commands and timing are not identical between the two, so the software in the device which communicates with the flash would have to be changed a bit. However, they both have identical pinouts, and assuming they can modify their code a bit to adapt to the SST39, it should be functionally equivalent and work in most applications.

[Travis_Weesner]

Alternative cross option offered:

@David_1528

I checked out a few other parts, and from what I can tell, the MX29F040CQI-70G looks like a nearly direct cross. The memory organization is the same (8 equal sectors of 64K bytes each) and the commands look to be identical. It will, of course have a different chip ID (C2h A4h rather than 01h A4h), and there may be some subtle electrical variations, but it most likely would work as a sub.