Hello Michael, SDCC will not magically start using the external memory when it runs out of internal. You have to place your variables there using the __xdata keyword. Or if you're lazy you can use the large memory model which places everything in external ram. Also have a look at --xram-loc and --xram-size to tell sdcc how much memory you have and where it is located.
If the hardware is not yet set in stone I suggest to also look at other microcontrollers which have "external ram" internally. This frees up many IO pins. Welcome to the 8051 Maarten > On 08/29/2013 03:19 PM, Michael Hawkins wrote: > > Please excuse my newbie questions. > > We've all gotta start somewhere. > > > I am working on a project that will use an 89C55WD which is an Atmel > > 8051 variant. > > > > I need more than the 128/256 bytes of RAM. I have seen that 8051 > > supports up to 64K or external RAM. > > Yes it does. > > > These two articles describe adding 64K of RAM. > > > > http://www.8052.com/tutmemor.php > > http://www.mikroe.com/chapters/view/65/#ch2.4 > > > > Is support built into SDCC for using the external 64K of RAM? Are there > > any flags or switches that I need to use to use external RAM instead of > > built in 128/256 RAM bytes? > > How the external RAM is implemented in hardware is not visible from > firmware. Just add it as you normally would, and tell SDCC to put stuff > there, and you're good to go. > > You can also use mcs51 implementations that have on-chip memory in > that address space, transparently. I've done bunches of work with the > Philips (erm, NXP) P89C66x chips, for example, which have "external" RAM > implemented in that fashion. > > -Dave > > -- > Dave McGuire, AK4HZ > New Kensington, PA > > ------------------------------------------------------------------------------ > Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! > Discover the easy way to master current and previous Microsoft technologies > and advance your career. Get an incredible 1,500+ hours of step-by-step > tutorial videos with LearnDevNow. Subscribe today and save! > http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.clktrk > _______________________________________________ > Sdcc-user mailing list > Sdcc-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/sdcc-user ------------------------------------------------------------------------------ Learn the latest--Visual Studio 2012, SharePoint 2013, SQL 2012, more! Discover the easy way to master current and previous Microsoft technologies and advance your career. Get an incredible 1,500+ hours of step-by-step tutorial videos with LearnDevNow. Subscribe today and save! http://pubads.g.doubleclick.net/gampad/clk?id=58040911&iu=/4140/ostg.clktrk _______________________________________________ Sdcc-user mailing list Sdcc-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/sdcc-user
