BGB100@psuvm.psu.edu (Bruce Blanar) (03/25/91)
I have a 520ST with a slight I/O problem: The machine will not read from the SS external floppy drive. To boot the machine, I must have the floppy drive turned on without a disk inserted. After the 30 or 40-second timeout, the desktop appears. If I try to open the drive A icon, or try to format it (in other words, access it in any way) the system crashes. By crash, I mean that the mouse freezes and only a reboot will free it. I was tracing the 68000 pinouts and it seems like the CPU is stuck in a bus grant state. If I understand it correctly, it seems to be granting the bus, but it never receives it back from whatever it granted it to. The function code outputs signal an interrupt acknowledge and the IPLx lines signal a level-6 (or is that a level-1?) interrupt. I don't know much about the ST internals as far as interrupts and the way that the floppy is interfaced (is it DMA?). I'm not sure why the CPU has granted the bus to another device which doesn't seem to want to give it back. Any help/suggestions that I receive on this would be greatly appreciated! -Bruce |\___/| Bruce Blanar |"Everybody need a mood lifter, |/. .\| Penn State University | Everybody need reverse polarity." | . | BGB100@PSUVM.bitnet | -Rush \___/ voice: (814)867-9079 |