Hello there,
I have a question for the assembly language specialists.
Below we see the 6809 code on the right and the timing diagram of the data bus on the left.
Can somebody confirm that the data which is read in the 6850 by the instruction "LDB ,X" is indeed $0C ?
We can clearly see $E684 then a $C5 (what is that ?) then $0C (the data read at address X
) then we see the $C502 of the operation "BITB # $ 02".
If the data is really $0C logically the program switch to END and the loop starts again and nothing is ever written in the output register of the 6850 ...
Finally if anyone has any idea why the TDRE bit of the 6850 is not to one after a reset that interests me a lot
Could that come because the CTS input (coming via a MC1489 line receiver) is floating ?
Have a good evening.
Philippe