reading bad internal SRAM data

aa · ‎2008-03-28

Posted on March 28, 2008 at 15:43

aa · ‎2011-05-17

Posted on May 17, 2011 at 11:52

Hello,

I use a UPSD3354DV-40u6 and have a problem with reading the internal SRAM.

After testing several pcb boards the result is that I have boards that read

corrupt data from the internal SRAM. After debugging I have seen that a wrong board

has a ''bad signal'' at the databus when reading at an adres in SRAM. With ''bad signal'' I

mean that it is not a nice ''1'' but a slow rising signal from ''0'' to ''1'' like loading a capacitor.

Other external busdrivers can drive the bus and are tri-state at the moment the SRAM is reading.

(seen with a scoop that triggerd on the \RD pin an looking at MCUAD0 (multiplexed databus 0)).

After some testing the board is working fine and it have a good signal.

Please let me know if you have some tips or suggestions to solve this problem.

Best regards,

AndrÃ©

aa · ‎2011-05-17

Posted on May 17, 2011 at 11:52

Hello all,

The problem is solved. The reasen was that the battery voltage (PC2) was sometime above the Vdd so thhe SRAM goes in protection mode.

Best regards,

AndrÃ©