DSC MC56F8357 External memory access problem

[tshah]

Hello community people,

I'm working on integrating external data RAM as well as Program flash with the DSC MC56F8357. I use CW 8.0 version for the external memory development. I'm facing problem to map the external memory to the external RAM even though I mapped the address of the data memory correctly as per the memory mapping details. I use CPU properties to configure or initialise the external memory for data RAM as well as external program Flash. I connected the /DS to the data RAM and /PS to the Program flash.

Now I'm trying to make the external RAM as my data RAM but its not working even though its configured through CPU properties - > External memory Buses enabled

My Current project Settings are given below for your references. I have attached the memory interface also for your reference.

Program Memory - Internal

Data Memory - External

Initialise OMR - Yes. (Tried with yes and No )

Kindly help me to make the external memory up and running.  All your comments and guidelines/notes are most welcome.

Thanks.

Regards,

AT T

[johnlwinters]

Try using wait states for the RAM.

Also, try setting the DRV bit so that the interface is always driven.

[tshah]

Thank you John for your inputs and the information.The Pseudo SRAM worked after I removed a memory mapped peripheral device that was multiplexed on the same bus.I used wait states for R/W operations and also set the drive bit.

Thanks again for the support.

[Ben]

Hello AT

I developed a project with the same configuration: same chip, internal program memory, external RAM for large data memory. It works good after manually changing the configuration file and adding #pragma in code, however, I worked with CW10.6 and not with the old 8.0.

As far as I remember, I had problems using the 8.0 and I switched to 10.x

If you agree to  import the project to 10.6 I can send you details.

[tshah]

Hello Ben,

Thank you very much for the information. Yes I agree, please send the detailsto import to 10.6

AT

[Ben]

In the project settings files open the linker command file (.cmd).

There are 2 changes you should add there:

1) define the external memory address range

(see the .x_ex_data from address 0x10000)

At the end of the file add the section definition:

Now you can use this memory section.

In the code file add the following pragma:

That's all!

After making the changes in the cmd file, make sure too disable the automatic linker file creation, otherwise it will overrun your changes every time you'll rebuild the project

[tshah]

Hello Ben,

I have configured the external bus for internal memory boot and support for internal as well as external data memory. I had multiplexed the bus between parallel NOR flash (CS0) from spansion and PSRAM (CS1) from ISSI. I can access the NOR flash but I couldn’t access the PSRAM.

I checked all the configurations and it’s correct. I doubt with my PSRAM is not supporting with the DSC. What SRAM do you suggest to use? I selected PSRAM for low cost reasons. It would be a great help if you can advise on this.

In my project I need only external data RAM (probably around 512KB). Please suggest which SRAM to go with

AT

[Ben]

Hello AT

I used ISSI RAM (see attached) and it works good.

Ben

[tshah]

Thankyou Ben.The Pseudo SRAM worked after I removed a memory mapped peripheral device on the same bus.Thank you for all the inputs and support.