I have a board that another engineer developed several years ago. He incorporated a monitor program into the board that allows me to download my own application to flash memory and then execute the application on resetting of the board. My application can call upon routines incorporated into his firmware. Internal ram is used for data transfer between my application and his routines. However he left gaps of unused internal ram. I found out how to prevent my routine from using the internal ram after address 0x7C so the C51 compiler wouldn't write over values needed by the firmware routines. Is there a way to reserve ranges of internal ram addresses so the C51 compiler can use those locations not required by the firmware routines?
How about the RESERVE linker directive? The manual doesn't say that it doesn't work on idata, at any rate.