18F87K22 & extended memory in PBP3

[longpole001]

Hi guys ,
am looking further at the above pic with the thought of extending the available memory with a 1meg Sram , and wondered if PBP3 supports the extend instruction set for when the code is compiled for ram expansion ?


I am also trying to find some examples how to setup and use it

Cheers

Sheldon

[longpole001]

PIc is 18F67k22 - My typo on Thread header

The datasheet talks about an extended memory map when using external memory bus

does PBP3 allow for an extended memory when used to be compiled for this chip , and if so is what is required

I am sure if i try and use more mem then 4k when setting up variables it would not work. unless i told PBP some how that external memory has been added and can use it for this chip/ application and then compile ??

Any information on this would be useful as i would like to use more memory for this application both in active memory and perhaps program memory than the base chip , which is designed to allow this to happen

Cheers

sheldon

[Darrel Taylor]

1. - The External Memory Bus is not implemented on 64-pin devices.
The 18F67K22 is a 64-pin device.

2. - The External Memory Bus extends the "Program Memory" space.
It does not extend the GPR (General Purpose RAM) space. So you cannot put PBP variables in that area.
But, you can use READCODE and WRITECODE to use that memory for data storage.
Although, you would need to use an 80-pin device, and compile with PBPL.

3. - PBP will not work with the "Extended Instruction Set" (XINST) enabled.
But the Extended Instructions have nothing to do with the External Memory Bus.
XINST affects FSR2, the Access Bank, and software stacks used by the C language.

[longpole001]

thanks darrel , for help and time to read


cheers

Sheldon

[longpole001]

darrel is there a way to extend the usable GPR space of any pic past that of the base pic with extra ram and using PBP3, if so which chips are suitable

[Darrel Taylor]

There are lots of ways to add more RAM to a PIC.

But none that I know of will allow PBP to put more variables in there.