ISD2115 write corruption (byte skipping during flash write)

[adel-ailane]

Issue

Writing a custom binary to the ISD2115 always fails verification.

After inspecting the written data, it appears that bytes are being skipped during write operations, leading to corrupted data and 0xFF padding at the end.

Observed behavior

Example 1

Written:

CF 0B 00 00 00 24 A6 00 48 A6 00 49 A6 00 67 A6 
00 68 A6 00 86 A6 00 87 A6 00 90 A6 00 91 A6 00 
9A A6 00 3E 00 00 B0 60 00 B1 60 00 23 A6 00 00

Read back:

CF 0B 00 00 00 24 A6 00 48 A6 00 A6 67 FF FF FF 
00 68 A6 00 86 A6 00 87 A6 00 90 00 A6 FF FF FF 
9A A6 00 3E 00 00 B0 60 00 B1 60 23 00 FF FF FF

Example 2 (pattern test)

Written:

00 11 22 33 44 55 66 77 88 99 AA BB CC DD EE FF

Read back:

00 11 22 33 44 55 66 77 88 99 AA CC EE FF FF FF

Notes

• The corruption pattern is consistent: it looks like every other byte is skipped after a certain offset
• The last bytes of each block end up as FF FF FF
• Erase and read operations work correctly
• The issue appears only during write
• I tested an ISD2110, and it works correctly with the same setup

Question

• Is ISD2115 known to require different timing or handling compared to ISD2110?

If needed, I can test modifications or provide additional logs.

Thanks.