PBP External Memory Bus Support

[ALFRED]

I am working on a project that will require large amounts of RAM. It has come to my attention that some of the new PICs include an external memory bus. Apperently, this bus is able to acces up to 2MB of data. I am wondering if the PBP compiler supports this feature. I appreciate any info on this.

[skimask]

I am working on a project that will require large amounts of RAM. It has come to my attention that some of the new PICs include an external memory bus. Apperently, this bus is able to acces up to 2MB of data. I am wondering if the PBP compiler supports this feature. I appreciate any info on this.

Do you need to use RAM? Wouldn't the huge 128M x 8 I2C eeprom chips (24AA1025, 24FC1025, 24LC1025 from Microchip) work? DIP, SOIC, etc.

Or for that matter, it is relatively easy to interface an SD card to a PIC, although the connector is a bit of a pain to work with.

And an external memory bus isn't a new thing, it's been out for years.

[ALFRED]

My project will be using SRAM. EEPROM or flash will not work since I will be constantly re-writing the memory. I understand that external memory busses have been around but on some of the microchip parts, there is a bus specificaly designed to interface with external memory. The PIC I am looking at right now is the 18F8722. This bus includes adress and data lines as well as other lines to control external memory. Acording to the PIC18F8722 data sheet, this bus allows the program to seemlessly work with the external memory. My question is, will PBP address greater amounts of RAM then what is included on the chip and if not is there anything I can do to make it do this.

[Darrel Taylor]

Well, Yes and No.

PBP can not access anything on the external bus directly. The compiler is limited to the first 64K of memory.
Which means that it can't even use the upper 64k of the 128k already on your 18F8722.

>> My question is, will PBP address greater amounts of RAM then what is included on the chip

The external memory can't be mapped to RAM space. It only extends "Program Space". But if the external memory is Static RAM, it can be read from and written to, by using the TBLRD and TBLWT instructions, the same as if you were reading/writing to Flash.

With a few ingenious ASM macros, you could easily create a program that uses that space for storage, but you can't do it directly with PBP.
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[Luciano]

Hi,

FRAM?

EEPROM and Flash devices have a limited write
endurance of typically 100,000 to 1,000,000 writes
compared to 1,000,000,000,000 or more for FRAM.

What is FRAM?
http://www.ramtron.com/doc/AboutFRAM/Default.asp

Serial Memory Products:
http://www.ramtron.com/doc/Products/Nonvolatile/Nonvolatile_list.asp?ID=5

Distributor:
http://www.mouser.com

Best regards,

Luciano