External memory bus & DPRAM do not work.......

[Twain]

Hi all

I've a design with a 18F87J10 and a 8 bit DPRAM connected over the external memory bus interface (8 bit design with hw address latch) .

I use the CCS compiler PCH 4.024 and want to use the integrated functions for the EMB access.

I activated these fuses:

#FUSES BW8 //8-bit external bus mode
#FUSES EMCU16 //Extended microcontroller mode,16 bit address mode
#FUSES EASHFT //Address shifting enabled

I also set up the memory IF with:

setup_external_memory(EXTMEM_BYTE_WRITE|EXTMEM_WAIT_0);

While performing a read_external_memory() call, I can't measure any changes with the oscilloscope on the control lines (CE,WRL,OE) and the address lines.

In other words, the device access does not work and I have absolutely no idea why.

Does anybody know about the problem?

Regards & thanks
Urs

[Ttelmah]

I'd suggest setting EBDIS yourself, in case the functions are not doing this.
What address are you trying to talk to?. Remember that the external memory begins at address 'top of memory+1', and with address shifting enabled, this internal address accesses address 0 in the external memory.
So your external memory starts at address 0x20000, with this addressing address '0' in the external module.

Best Wishes

[Guest]

Many thanks for your suggestions.

My problem was indeed that I did not take care about the 0x20000 offset. I assumed to have external base address at 0x00000 (with address translation within the calling function) due to activated address shift.

Now I can get the signals toggeling and also read correct data...

Urs