Hello Bart, I agree with Bodo. Xdata is probably not set up correctly. Does your mcu have internal xdata? And do you need to enable it? Otherwise I expect your real external ram not to be working.
You should not need to initialize malloc, it's probably ok. Greets, Maarten > Hi Bart, > > Your analysis is well done, and I appreciate your assembler knowledge. > > However, I'm not sure that I do understand what you mean by "Gives nothing > on the output port P2." For the moment I assume that each line of P2 > doesn't change its level, i.e. it stays at "1" which is the default after > a reset. So it's possible that P2 is written with 0xFF. > > BTW, you can check such a write with a pulldown resistor that lowers the > voltage at a pin down to 3/4 or 1/2 of VCC. An oscilloscope will show the > write access with a small impulse to VCC because the 8051 ports will > reduce the builtin pullup value for two clock cycles. > > My suggestion for the next steps would be: > > If you can't use a simulator with the hex file, and if the only watchable > output is P2, > > 1. Run three tests, each setting P2 with one byte of the generic pointer. > > 2. Check that the external (or internal?) memory at that address is > working or at least should be by the schematics. > > 3. Invert the value before assigning it to P2, like "P2 = ~*stream;" I'd > expect then every bit at "0". > > If you have a simulator at hand, run the program with it. Well, you will > have to step through the builtins, but perhaps the simulator can run a > subroutine as one step. > > Another issue is the malloc stuff. I'm not using SDCC currently and so I > don't know how it works here. But I played a bit with z88dk, and there I > had to set up malloc with some special functions and variables to get it > working. > > To say it shortly, these are the two most probable reasons: > > - The memory pointed to by the return value of malloc() can't store > anything > because of a hardware problem. So a read from it returns 0xff which can be > the value of an open databus. > > - malloc() returns an arbitrary but reproducable pointer because the > allocation management is not initialized. And the memory pointed to can't > store any value and always returns 0xFF. > > Bodo ------------------------------------------------------------------------------ _______________________________________________ Sdcc-user mailing list Sdcc-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/sdcc-user
