SDRAM problem on PPC405EP

I have a design on PPC405EP processor.

In my design, a 2M * 32 bit SDRAM is used. But in practice, Only One type
of SDRAM chip is supported, other Chip can not work in same configure.

I set the SDRAM config register as the following:
#define SDRAM_CFG 0x80800000
#define SDRAM_RTR 0x08200000 /* Define 133M refreshing rate. 133MHz
#define SDRAM_B0CR 0x00828001 /* 8M, Base=0x800000(8MB) */
#define SDRAM_B1CR 0x00028001 /* 8M, Base=0 , Mode 5 (11 * 8 * 4) */
#define SDRAM_TR 0x018FC01B

EM638325 which made by ETRON Co. is supported, The other chip can not
work. Such as: K4S643232, W986432, 48LC2M32, VT3664324, and so on, they
all have -6 ns feature, working properly at 133Mhz on other system. I have
check the data *** of these chip, they are compatible and suitable for
the actural configure.

But after many times trying, the other chips can not work properly.
The problem is like the following:
First write Data1 to Address1, and then write Data2 to Address2,
Third, Read from Address1 and Address2, the result is both Data2.

Because the EM638325 is difficult to purchase now, I need a replacer.
Please help me.

Thanks and Regards.

Rivor Wang



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