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Discussion Groups | LPC2000 | LPC2458 external memory
Discussion group dedicated to the Philips LPC2000 family of ARM MCUs
LPC2458 external memory - dave_albert - Oct 17 8:07:43 2009
It is not entirely clear from the datasheet, but it appears that the LPC2458 external
memory controller (EMC) is limited to addressing two 1MB blocks of external asynchronous
static memory such as parallel flash or SRAM due to the 20 address lines; it can also
address two larger blocks of SDRAM, but the static memories are limited to 1MB each. Is
this correct?
When using external 16-bit-wide memory parts, only address lines A1..19 are used (A0 is not used) and individual byte addressing is done using the /BLS0 and /BLS1 pins. Can anyone confirm this?
Finally, are there any limitations to the use of external RAM? For example, can data in external RAM be written to on-board flash using the IAP flash API (I know that internal special-purpose RAM such as RAM reserved for Ethernet or USB buffers often cannot be used this way in the LPC2xxx series)
If anyone has experience with asynchronous external memory for the LPC2458, I'd be grateful if you would share your experiences. Thank you!
------------------------------------
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When using external 16-bit-wide memory parts, only address lines A1..19 are used (A0 is not used) and individual byte addressing is done using the /BLS0 and /BLS1 pins. Can anyone confirm this?
Finally, are there any limitations to the use of external RAM? For example, can data in external RAM be written to on-board flash using the IAP flash API (I know that internal special-purpose RAM such as RAM reserved for Ethernet or USB buffers often cannot be used this way in the LPC2xxx series)
If anyone has experience with asynchronous external memory for the LPC2458, I'd be grateful if you would share your experiences. Thank you!
------------------------------------
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Re: LPC2458 external memory - rolf_meeser - Oct 17 9:14:30 2009
Hi Dave,
--- In l...@yahoogroups.com, "dave_albert" wrote:
>
> It is not entirely clear from the datasheet, but it appears that the LPC2458 external memory controller (EMC) is limited to addressing two 1MB blocks of external asynchronous static memory such as parallel flash or SRAM due to the 20 address lines; it can also address two larger blocks of SDRAM, but the static memories are limited to 1MB each. Is this correct?
>
Yes.
> When using external 16-bit-wide memory parts, only address lines A1..19 are used (A0 is not used) and individual byte addressing is done using the /BLS0 and /BLS1 pins. Can anyone confirm this?
>
That is correct. You can find an example at the end of chapter 5 of the user manual.
> Finally, are there any limitations to the use of external RAM? For example, can data in external RAM be written to on-board flash using the IAP flash API (I know that internal special-purpose RAM such as RAM reserved for Ethernet or USB buffers often cannot be used this way in the LPC2xxx series)
>
External memory cannot be used as the source in the "Copy RAM to Flash" IAP call. Only internal SRAM on the local bus (0x40000000) can be used.
Regards,
Rolf
------------------------------------
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--- In l...@yahoogroups.com, "dave_albert"
>
> It is not entirely clear from the datasheet, but it appears that the LPC2458 external memory controller (EMC) is limited to addressing two 1MB blocks of external asynchronous static memory such as parallel flash or SRAM due to the 20 address lines; it can also address two larger blocks of SDRAM, but the static memories are limited to 1MB each. Is this correct?
>
Yes.
> When using external 16-bit-wide memory parts, only address lines A1..19 are used (A0 is not used) and individual byte addressing is done using the /BLS0 and /BLS1 pins. Can anyone confirm this?
>
That is correct. You can find an example at the end of chapter 5 of the user manual.
> Finally, are there any limitations to the use of external RAM? For example, can data in external RAM be written to on-board flash using the IAP flash API (I know that internal special-purpose RAM such as RAM reserved for Ethernet or USB buffers often cannot be used this way in the LPC2xxx series)
>
External memory cannot be used as the source in the "Copy RAM to Flash" IAP call. Only internal SRAM on the local bus (0x40000000) can be used.
Regards,
Rolf
------------------------------------
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