Hi,
Im trying to interface two 128Mbit SDRAMs (MT48LC8M16A2) to the AT91RM9200, but it doesnt seem to be going right. I have a custom board for the AT91, and a seperate board for the SDRAM, the two are connected through an ordinary ribbon cable.
The master clock of the uC is running at 60Mhz. To test the integrity of the RAM, im writing data to a series of locations, say from
0x2000_0000 to 0x2000_0100. But when i read the data back, i find it to be garbled at *many* locations. I mean, instead of 0x11111111 that im writing, i get a 0xEff1111 or something at some locations, while on others the data is perfect. (im sending data out from the debug unit to HyperTerminal for debugging)I have tried all permutations and combinations of the initialization sequence, but to no avail. Even tried changing both the ribbon cables (ive got one for the address lines, another for the data). What could be going wrong?? I dont think any of the SDRAMs has gone bad, because they both seem to have the correct data sometimes.
COuld it be because of the fact that im using a seperate PCB for the RAM chips??
Thanx in anticipation Mayank