From: Marko Mäkelä (marko.makela_at_hut.fi)
Date: 2003-01-27 19:03:21
On Sat, Jan 25, 2003 at 10:25:08PM -0500, William Levak wrote: > Sounds like you have a bad data driver. The Am29F040 chip in the prototype is partly directly connected to the VIC-20 cartridge port. D0-D7 and A0-A12 are connected directly to the cart port, while other signals go through the Lattice 2032 programmable logic chip. I just got the memory dump of the chip (made with a universal programming device). After deshuffling the address and data bits in the image, I got a file whose first 8k bank looks identical to what I read from the VIC-20. All of the remaining 504 kilobytes are $ff. This suggests a software problem. The strange thing is that all other bytes except those $ff are written correctly. And my program verifies each byte written by reading the same address until the data matches. It appears that the bytes are changed later by the program. I guess I'll have to apply binary search to narrow down the address where the error occurs. > I've never run into one where all the bits had to be high in order for the > write to fail, but I have had drivers that failed when particular bits were > high. There is a pattern in the data: bits 0 through 2 (as seen by the VIC-20) appear to be affected. On the 29F040, those would be bits 6, 7, and 5. Marko Message was sent through the cbm-hackers mailing list
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