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
As have been mentioned long time a go - yes, if it is supported to configure the memory controller for use with a 16-bit memory you obviously have to do that. If it isn't supported, you are busted.
Next thing - if the memory controller supports 16-bit wide memory, then it will allow the processor core to perform 32-bit accesses. These 32-bit accesses will be converted into two 16-bit accesses to they memory. All the difference it makes to the processor core is that the memory accesses will be slower because the two 16-bit accesses must be made after each other.
"... because processor data sheet do not mention anything about it."
What processor information are you looking at?
In UM10326, section 7.2 (Features of the EMC) it states:
• 16-bit and 32-bit wide SDRAM memory support
That same chapter also has a note that says:
For SDRAM chip selects that are configured for 32-bit wide transfers, single SDRAM bursts are used. When SDRAM chip selects are configured for 16-bit wide transfers, a burst length of 2 is used. Mode registers in related SDRAM devices must be programmed accordingly.
Table 115 has a good table too.
Plenty for you to check out.