#ROM directive; string problem; compiler bug?

JR · Guest

I want to use the #ROM directive to insert string data into the code space, but the compiler seems to get it wrong!
For example if I put :-

Ttelmah · Guest

Remember ROM addresses, are _word_ addresses.
On a PIC18, you can fit two string characters in each word.
As far as the compiler is concerned, you are writing a 16byte string into 16bit wordspace, so only 13 words need to be reserved. You are electing though to write the data to alternate bytes, which the compiler does not understand....

You need to either add the int8 keyword to your ROM statement. So:

#ROM int8 ROMDATA={"900-DV-6050-000 HAMSTEr\n"}

Which will then put the data sequentially into the _bytes_ of the ROM, or store the individual characters, not a string.

Best Wishes

JR · Guest

Oops, I forgot to mention, it's for a 16F884 (using V4.093 compiler).
That gives me 14 bit data so the compiler shouldn't/can't pack 2 characters per word -
and it doesn't; the hex data shows that the compiler actually generates the strings correcly, it just gets the length wrong when it's linking all the code together.

As it happens I'd already tried declaring the data as int8, and as int16 - it makes no difference

Ttelmah · Guest

It is a bug, and I'd report it to CCS.
With a PIC16, you can use the 'char' option to pack two 7bit characters into each 14bit word, but given this is not the default, I'd have expected the compiler to have correctly handled the sizing...

Best Wishes