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DM6437: What will be refresh rate if cusotmer writes a DDR2 refresh rate values <= 1.95 us?

MJovi
Intellectual 2465 points


Hi,

I have a question on interfacing DM6437 with DDR2 memory- W3H64M16E-400BM (MicroSemi).

Customer is required to run the DDR2 at 125 degrees temperature and  need to configure the DDR2 controller of the DM6437 to operate at different refresh rate (  <= 1.95 us).

From the data sheet of the DM6437 DDR controller, it seems to be possible to configure at various refresh rates. Ref- spru986c (section-4.3) SDRCR (RR fields).

- But it is not clear about the minimum refresh rate that it can be configured (100h will be 1,9us).  How it behaves for refresh rates resulting RR value < 0x0100h?

According to user guide mentioned above writing a value <0100h to RR, RR will be loaded with the value 2 X T_RFC from SDRAM timing register (SDTIMR), which is not the same as RR.

For example, what will be the refresh rate when they write a value 0xA0 to RR( DDR2 clock is 133Mhz)? (RR should be 1.2us)

 

Thanks and Regards,

Majda