EEPROM WP

[memaher]

Got a problem programming the EEPROM, its rather strange…

On my first revision of board, the EEPROM WP line was tied to Vss through a switch. I then used a dirty u-boot to manually program the EEPROM using uboot’s i2c md/mw commands. This worked.

On my second iteration of board, I got clever – which is where the problems started. The I2C line and WP are tied to my MSP430 power supervisor with the intention of automating the EEPROM programming for manufacturing. However, I am now in the situation whereby the EEPROM cannot be programmed via any means:

programming via the MSP430 shows valid I2C commands (with ACKS): yet nothing is programmed when read back – all 0xFF’s.
programming via dirty u-boot shows the same problem: writes are accepted but on readback nothing is present.

Everything is scoping out ok: WP is low when it needs to be low.

I can only assume this must be a timing/latching problem.

Q. Can you confirm what power source the EEPROM is connected to, and what the minimal power-on-sequence is needed to power the EEPROM (without powering anything else)? I’m thinking the difference in setup is that the MSP430 starts high-impedance compared to a manual switch…

Q. Have you ever had manufacturing failures on these EEPROMs being duff?

q. What is the internal pullup on the EEPROM WP line (maybe I’m not driving strong enough)?

any thoughts/suggestions appreciated.

Mat

Q. Are you aware of

[memaher]

Resolved: needed to change the external pullups (2k2 now) on the I2C line.

[Author]

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