Prasad, Satyaprakash wrote:

> When we say that it is a PIC of 12,16,17 or 18 series, is it that we
> actually mean to differentiate it with the memory bit it can address at a
> time.

First, note that the PICs uses Harward architecture (separate
program and data storage), not the more common von Neumann type
(with a common address space for program and data).

The program storage on PICs are 12, 14 or 16 bit wide ("instruction word").
The data storage on PICs are always 8 bit wide.

> Example PIC 18 series can fetch and process 16bit instruction at a
> time, similarly PIC 12 series executes 12 bit.

More or less, bit it is not that simple. There are PIC12's that
has both 12 and 14 bit wide instructions.

> In this case how many bits a PIC instruction would be(8,12 or 16)bits?

Depends on which model you are talking about. Could be 12, 14 or 16 bits.

> Is it possible that an application developed for PIC 12 could execute
> on PIC 16 series.

You surely have to make some changes to the source and recompile.
And, the older PICs are so different from the newest, so you'd
probably redesign the application from the start anyway...

> And what exactly we mean when we say PIC can address 16 bit at a
> time? Is the memory addressed in RAM or ROM are they talking about?

Some PICs (18-series) can address 16-bit instructions (ROM or Flash).
All PICs addresses 8-bit data (RAM or EEPROM).

Jan-Erik.

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