| ??? 05/19/07 23:01 Modified: 05/19/07 23:02 Read: times |
#139545 - Tables in code space vs data space Responding to: ???'s previous message |
Erik Malund said:
If you guys want to argue about off-chip resources, go ahead. It won't help speed up anyone's code, though.
Are you saying that you can not write (in)efficient code for accessing external resources? No ... it's easy enough to do it for either. I'm just pointing out that the original context in which I pointed out those instructions which are useful for table lookups but which work only in code space, and not in XDATA, are part of the original discussion, but not this one which has wandered off into XDATA. Your assertions are correct. You can, indeed store both table and other data in XRAM. You can't store code there, though, and the comment I made about where you would likely store tables. I don't know how big an advantage storing tables in XRAM as oposed to code space would be, regardless of whether the code space is internal or external, but it offers those additional instructions that are really handy for table lookups. BTW, with which MCU are you using those DALLAS BBRAMs? How much code space does it have? The thread is "How to speed code?" NOT "how to use internal resources efficiently".
As a matter of fact I once had a thingy with two of the battery backed Dallas NVRAMS one was the bootloader with the remainder free, the other was the app which used the space above the bootloader as XDATA. To boot, switch the two memories, to run, switch back. Yes, I have one like that on the bench right now but only using one BBRAM. I dump 'em into fast SRAM so they'll be quick enough for my MCU. Erik I doubt you'd use up your internal code space unless you already had tables in it. RE |
