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
