Buffers & Memory

[guest]

Hello all,

I've got an existing program that I've implemented the ring buffer example into on a 16f877 and it works great. I'm reading an 84 character string in the RS232 port and combining it with existing data I'm sending back out the RS232 port. The issue is that it seems 80 is a magic number for the buffer size declaration and I need closer to 90. If I go over 80, the memory usage goes up significantly when I compile and I'm running out of room. Is there an easy way to solve this? Am I going over banks of memory at 80?

thanks much.

[PCM programmer]

Yes there's a limit to the RAM bank sizes. Read the data sheet.

It's possible that you could put your buffer into bank 2 or bank 3,
which have 96 bytes each, without encroaching on the common
ram at the end of each bank. You could use the CCS functions
read_bank() and write_bank() to access this area. This assumes
that you're not using the #device *=16 directive, so that the
compiler won't be using those banks.

See the CCS manual in the read_bank() section. It has a description
of this exact problem, though it's for the older 16c57 series.

I've never done this, so I don't know if the ROM savings is worth
the effort. Most people on this forum will suggest that you upgrade
to the 18F series, which will eliminate the whole problem because
they have much more RAM, ROM, etc.

[treitmey]

This one is 112 and compiles to 3%ROM 29%RAM which seems about right for the data sheets. Note the largest size is 16+80+16=112.