Strange zero reading on Olivetti Prodest PC128

C'est la catégorie reine de l'ordinophile, 8 bits et pas un de plus!
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Inscription : 24 oct. 2021 15:47

Strange zero reading on Olivetti Prodest PC128

Message par spotlessmind1975 »

Good morning everyone. :D

I am having some trouble reading K7 files larger than 256 bytes and I hope someone can help me. Specifically, the routine I set up and which should read a file one block [256 bytes] at a time from the K7 at $9000 and, then, move it into memory as a contiguous "file" starting at $6000, introduces zero (0) at the start of the block thus replacing the legitimate value. I made sure, with a hex editor, that the values were there in the K7 (clearly they are not consecutive because between one block and another there is a header).

For the sake of clarity, I had never noticed the problem because, generally, these blocks contain bitmap graphics. So basically, I found that 2-4 pixels of the background were black so I didn't notice. Now, however, I am using blocks to store the result of a compression routine and that 0 is, semantically, very relevant. :shock:

Thanks everyone for any help! 8)

The code that loads the block can be found here: ... p.asm#L106