CCS Build & Run without erasing entire flash area.

allenhuffman · Posted: Tue Jun 01, 2021 11:51 am

This is related to bootloader research I was doing in 2020:

http://www.ccsinfo.com/forum/viewtopic.php?t=55241

I have a CCS program that is my bootloader, which contains a stub app at memory 0x4000 (just blinking LEDs).

It can be loaded and will run the stub app just fine.

I then want to Build & Run a second project, which is the application code that should load at 0x4000 and do the real work.

After not getting this to work, I remembered the issue where it would first erase the flash part, wiping out the bootloader.

At the time, you could not do this manually in CCS Load. There was an option to NOT erase the flash, but CCS confirmed that it was not working. It may be now, but what we want to do is:

1) Build & Run the bootloader code (0x0000 - 0x3fff range, for example).

Then during development, we'd like to just:

2) Build & Run the application code (0x4000 - ???).

Doing step #2 erases everything from 0x0 to 0x3fff wiping out the bootloader.

I thought someone gave me a workaround two years ago but I haven't found the post yet.

Anyone recall? Or know how to do this?
_________________
Allen C. Huffman, Sub-Etha Software (est. 1990) http://www.subethasoftware.com
Embedded C, Arduino, MSP430, ESP8266/32, BASIC Stamp and PIC24 programmer.
http://www.whywouldyouwanttodothat.com ?

temtronic · Posted: Tue Jun 01, 2021 2:54 pm

Hmm....isn't there some 'FUSE' to write protect the bootloader segment of memory ?

allenhuffman · Posted: Tue Jun 01, 2021 3:00 pm

By default, CCS Load erases the entire memory first. There's a checkbox in the CCS load .exe to change this (which may or may not be fixed).

Support replied with this option:

temtronic · Posted: Tue Jun 01, 2021 4:49 pm

I don't use CCS Load,
but am concerned that the 'programmer' device OVERWRITES the actual program 'fuse' selections.
sounds like another 'wizard' that won't allow YOU to do what YOU want....
have to wonder what ELSE it's changing .....

Ttelmah · Joined: 11 Mar 2010 Posts: 19535

Obvious comment.
The 'second' program being loaded, should have:

#FUSES NONE

To ensure it does not override the existing fuses...

temtronic · Posted: Wed Jun 02, 2021 4:28 am

ah but what if CCSLoad decides to add it's OWN fuses.....?

Ttelmah · Joined: 11 Mar 2010 Posts: 19535

CCS_load, doesn't, unless you specifically change them.

Now, I'm not actually sure if he is using CCS_load 'directly', or via the
CCS IDE?. It does behave differently in the two cases. If you use CCS_load
'directly', the button to prevent erasing does work. However with a huge
'caveat', that if you load anything at all into a page, that whole page is erased.
It's only take something like a const stored near the bottom of memory, or
the delay code loaded down here, to result in the whole bottom page being
erased.
When instead you use it through the IDE, the program switches to a default
setting that CCS have selected. This does automatically erase the whole
memory. It is this that the command line option that the poster has been
given 'overrides'. Now, while CCS_Load (operated directly) will not set
default fuses, I don't know what it will do when driven from the IDE.
Would have to have a play with a chip and see.