Path: utzoo!attcan!uunet!wuarchive!decwrl!shelby!msi-s0.msi.umn.edu!sctc.com!briel
From: briel@sctc.com (Marc Briel )
Newsgroups: comp.sys.m68k
Subject: Re: Interpretation of 68000 Function Code Outputs
Message-ID: <1990Oct3.150536.6378@sctc.com>
Date: 3 Oct 90 15:05:36 GMT
References: <1057@tharr.UUCP>
Organization: Secure Computing Technology Corporation
Lines: 11

>
>What is the difference between program and data?
>
>.. from the point of view of both the processor and the user.


The processor uses the "Program Space" function codes for all instruction fetches and PC-relative (addressing mode) operand reads. Writes to program space never occur in normal instruction processing but they can be generated by the MOVES instruction in Supervisor Mode by placing the appropriate function code in the DFC (Destination Function Code) register.

Most commercial 68xxx based systems ignore the distinction between Program Space and Data Space in both the hardware (i.e. both program and data map the same physical memory) and in the software (memory management, seperating read and execute permission, etc.)

				Marc Briel
				briel@sctc.com