The MPC5746C RAM area data was unreadable if not initial after a reset happen

[madayzhang]

Hello everyone,

Why does the RAM area data could not been read if not clear after a reset happened, how should I set? In my application need some RAM data area could not been cleared except power-on reset, thanks.

[petervlna]

Hi,

This is proper behavior.

The RAM apply ECC protection. So if you destroy the RAM content there will be ECC fault in your RAM as the data will not match the syndrome. So you have to first initialize RAM and then you can use it.

For Power on reset or destructive reset, you will always loose RAM content, due to its power loss.

For external reset (JTAG) you can prevent loosing data by disabling the MBIST. (memory test during reset which will apply the testing ;pattern into RAM and destroys its content. As tenting do not use ECC, syndromes are not programmed)

regards,

Peter

[madayzhang]

Add more comments, the reset type was JTAG reset, are there anyone has the same problem and how to fix it, thanks.