LPC43xx External Static Memory - Read/Write buffering

[lpcware]

Content originally posted in LPCWare by lochkartenman on Wed Oct 01 10:52:05 MST 2014
We would like to tightly-couple a FPGA with a µC by means of the external static memory memory controller, thereby effectively mapping the FPGA registers into main memory of the µC with maximum bandwidth. At the moment we plan with 8-bit address & data and async. static NOR like interfacing.

For this setup it is necessary that each and every read/write is actually transmitted to the FPGA (memory) device and no buffering takes place. Since I am still new to the the LPC43xx family I wonder whether disabling buffers in the Static Memory Configuration registers is sufficient.

[lpcware]

Content originally posted in LPCWare by lochkartenman on Thu Oct 02 02:29:24 MST 2014
Many thanks. That puts the NPC43xx into a different light - I'm afraid I've been mislead by the stunningly short errata sheet. Apparently the STM32F4xx are comparable in terms of cavecats. What a pitty.

[lpcware]

Content originally posted in LPCWare by hlsa on Thu Oct 02 01:20:39 MST 2014
Be careful!

I have fallen into this trap by my own, trying to attach the AD7609 to the LPC4357 (in parallel I have a SDRAM connected to the EMC).
It resulted in a desaster:
[list]
  [*]My ADC has no adresses. Accessing the same address twice results in not reading the second time. I increased the address of my access pointer in order to make the EMC believe, that the address has changed. This worked, but: You cannot use this, if you need addresses.
  [*]For some reason (which I don't really understand), the EMC performs 8 consequent read accesses to the ADC, then it makes a long break, before the next 8 consequent reads are performed. Since I need my ADC data in realtime, this is not applicable for me.
[/list]
At the moment I am doing a redesign, where I will attach the ADC via SPI.


You should read this thread:
http://www.lpcware.com/content/forum/emc-generates-double-read-cycles-static-chip-selects

Best regards,
Holger