AM335x GPMC MRAM access issue

Kummi

Other Parts Discussed in Thread: AM3357

Hi,

We are using AM3357 in our custom board.
AM335x GPMC is used to connect FGPA and 2 MRAMs(Lower Byte & Upper Byte).
Everything is working fine except the 8 bit MRAM (MR2A08AYS35R).

The Data and Address bus are connected directly from GPMC to MRAM
but the control signals(BE0,BE1,CS,RE) are connected through FPGA.
The MRAM is used to store some data in the application.

Problem:
We are able to read/write the Lower Byte(BE0n) MRAM
but cannot read/write the Upper Byte(BE1n).

We tried to measure the voltage of Upper Byte of data bus and it was
1.5V(during active), but the Lower Byte was normal(3.3V).

Please let us know if anyone has used MRAM with AM335x & any pointers to solve this issue.

Best Regards

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

You should check the VDDSHVx voltages for the upper byte GPMC pins. Are you sure these pins are on a 3.3V voltage rail? Check Table 4-1 in the AM335X Datasheet to see which VDDSHVx rails supply the GPMC pins.

0 Kummi over 10 years ago in reply to Biser Gatchev-XID

Mastermind 6220 points

Hi Biser,

Thank you so much.

We cross-cheked your suggestion and all the VDDSHVx rails were 3.3V.
Could you please let me know what else could be checked in this case.

Apart from MRAM, NOR Flash(16 bit), FPGA(16bit) and a ethernet controller(16bit)
is connected to the GPMC.

Best Regards

0 Biser Gatchev-XID over 10 years ago in reply to Kummi

TI__Guru**** 393215 points

Probably one of these devices is pulling the lines. I cannot say without seeing the schematics. If you require a schematic review please contact your nearest TI representative.

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AM335x GPMC MRAM access issue