| ??? 08/09/07 08:21 Read: times |
#142961 - AT89C51RD2 Responding to: ???'s previous message |
David Prentice said:
Denis B said:
ok. thanks
i work with the AT89C51RD2.... according to data sheet it has – 256 Bytes Scratch Pad RAM.... i want a "small memory model", but keil "moved" me to "compact" after i get: Program Size: data > 128..... another question: how i define to keil 256 bytes? thanks If you read the various 8051 bibles, you will see that you can never have a large contiguous space in data. I believe that your RD2 chip has 1024 bytes of internal xdata. So you will need to examine your variable use to see what to place in idata or xdata. As a general rule, place large buffers in idata or xdata. Fastest access is to data, so reserve for frequent use. You can NEVER get 256 contiguous bytes in idata because the stack must live there. The Keil documentation is pretty good, as is the Hitex primer. ok, but according to data sheet: • 80C52 Compatible – 256 Bytes Scratch Pad RAM • On-chip 1792 bytes Expanded RAM (XRAM) – Software Selectable Size (0, 256, 512, 768, 1024, 1792 Bytes) – 768 Bytes Selected at Reset for T89C51RD2 Compatibility keil after 128 bytes data in small memory model requests to move to compact model, but where 128-255 bytes of idata?? |
