Continue to Site

Welcome to

Welcome to our site! is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

16 bits access external memory (PIC18F8722)

Not open for further replies.


Junior Member level 2
Dec 29, 2011
Reaction score
Trophy points
Activity points
Hi all,

I am initiate a new project, with 18F8722, greate PIC, I liked so much....

My intention, is use as microprocessor, but using then "extended mode" (Using too the internal flash memory). I just completed first part os project. RS232, Serial EPROM/RAM and Ethernet its all working vry fine.

Now, In the second part of my project, is use external memory, for data memory and fetche instruction (In External Flash Memory and RAM), but I vry familiarized wiht microprocessor 8 bits (16 bits internal archteture). But in this 18F8722 its a bit diferent (or MUCH diferent). I explain: I read many documents, PDF's, datasheets, and all its very similar, but any1 have one better explanition. For sample, I dont know how archteture I will to use (Word Write Mode, byte Write Mode, Byte Select mode and 8 bit byte mode). I understand wich all these model is similars. All use same Idea. the 16 bit types read 16 bits at once, its ok, but at address and at write mode, its very confuse:

All modes, have to connect A0 to A19 from uC to A1 to A19 Memory... Its very diferente for me this new logic.....

For simplify, I thinked to use 16 word write mode, but this mode, too use the idea above... I understand that A0 its the select byte, but in 16 world write mode, I thinked that, using 1 memory of 16 bit's or 2 memory with 8 bit's each (its my case, but configured to 16 bits mode), I can connect A0 (uC) to A0 (Memory)... Same in sample to mode 16 bite byte write mode, that connect A0 to A0 its confuse, and use BA0 to select where to write.....

In 8 byte mode, its more confuse, because for fetche, the uC use BA0 to retrieve instruction. WHY dont read 1 part of instruction at time ? Afffff....

Well... My idea is:
uC - 18F8722 connect with external memory (flash and RAM), 2 each with 8 bit's configured for 16 bit's, i wich mode ? i dont know. Someone have sample or schematic os c code (c18 or any1 other (htc, ccs, basic, pascal, fortran, delphi, dbase, cliper, rssss) that i translate) or any1 else for helpme ?

Ty a lot
Moacir Jr.

Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to