Hi All,
We have interfaced 1 SDRAM to LPC3250 (Lower 16 bit data line) .This SDRAM is from Micron technolgies 32 MB(MT48LC16M16A2).
Now problem is that we are not sure whether ,can we run our application code from the SDRAM ,because access from processor will be 32 bit wide , since we didn't connected anything on upper data line we will read junk values .
After seeing the refrence schematics provided by NXP we concluded that there is mistake in our hardware we should have connected 2 SDRAM (one on upper 16 bit and othe on Lower 16 bit) .
Question :
Is there still some way to run our code , can we build our code with THUMB instruction (16 bit)and run the code.
Please give your valuable feedback.
Thanks & Regards Sumit
memory controller support both 16 and 32 bit wide SDRAM support .
But why it fails if it support both ,can you please elaborate it.
If it has support for just 16-bit data width, then it must also have a configuration setting informing it that you only use 16-bit data width. Have you found such a configuration, and made sure it is correct?
Hi all,
We configured LPC3250 to 16 bit mode but still we are not able to write into locations which are multiple of 2 as seen in log. Write operation is short (16 bit) ,below are the logs of write and read to SDR-SDRAM.
Only one SDR-SDRAM is interfaced to LPC3250 on
Chip select - EMC_DYCS0 Data Bus D0- D15 Address Line A0- A14 EMC_DQM0 EMC_DQM1 EMC_CLK EMC_CLKEN EMC_RAS EMC_WR EMC_CAS EMC_CLK
Write : Mem Loc: value 0x80000000 0x1111 0x80000002 0x2222 0x80000004 0x3333 0x80000006 0x4444 0x80000008 0x5555 0x8000000A 0x6666
Read : Mem Loc: value 0x80000000 0x1111 0x80000002 0x1111 0x80000004 0x3333 0x80000006 0x3333 0x80000008 0x5555 0x8000000A 0x5555
Please throw some light on the matter
To the earlier post we would like to add another observation
if write happens only on location which are offset of 2 starting from 0x80000002, when we are reading nothing is written into memory please refer below log for clarity
Write : Mem Loc: value
0x80000002 0x2222 0x80000006 0x4444 0x8000000A 0x6666
Read : Mem Loc: value 0x80000000 0x33cc 0x80000002 0x33cc 0x80000004 0x33cc 0x80000006 0x33cc 0x80000008 0x33cc 0x8000000A 0x33cc
"But why it fails if it support both ,can you please elaborate it"
"Please throw some light on the matter"
You must configure both the controller and the SDRAM correctly. There are plenty of combinations that don't work correctly - Looks like you've got one of them.
But if it is configuration problem then we should not write a single location properly,Can you provide any link where we can find some code (tested) where LPC3250 is interfaced with SDRAM on 16 bit interface for cross checking our code.
"But if it is configuration problem then we should not write a single location properly"
That is not correct. There are many configuration combinations - Some of those can appear to partially work.
If the processor thinks the memory interface is 32 bit wide but the interface is only 16 bit wide, you obviously have a good change that a 4 byte wide write at first address of the memory will result in two of the bytes being correctly saved (since they map to the existing 16 bits) and two bytes fails to save. If you only test using 16-bit integers, you will not notice this.
Don't be so quick making assumptions. Only assume what you can prove. What you can't prove should be downgraded to maybe a suspicion. After all, a large percentage of all software errors are caused by people who have made incorrect assumptions.