Posted By
siz
on 2012-04-23
03:29:32
|  Re: 1551 ?Device not present error
Make sure to switch the 1551 on BEFORE the computer because the reset routine in the computer KERNAL does the initialization of the interface chip of the 1551 paddle.
Device not present means that the computer cannot communicate with the drive. It should be working without a functional drive mechanics.
Check if the 1551 paddle is visible in the plus/4 address space. For example in monitor m fec0 feff repated several times should return a stable value in either fec0-fecf (device #9) or fef0-feff (device #8) ranges. (for example clear the screen and enter the statement to the top then press home and return several times)
An example result from yape:
M FEC0 FEFF
>FEC0 00 00 00 00 00 00 FE FE :Ţ®Ţޮ֮Ţ
>FEC8 00 00 16 FE FC FE FE FE :®Ô®®®®®®
>FED0 FE FE 00 00 00 FE 17 70 :®®®Ţ®®®®
>FED8 FE FE FE FE FE 00 00 00 :Ţ®ŢޮޮŢ
>FEE0 00 00 C0 FF 00 40 00 00 :®®€ß®€®®
>FEE8 00 00 C0 FF 00 40 00 00 :®®€ß®€®®
>FEF0 00 00 C0 FF 00 40 00 00 :®®€ß®€®®
>FEF8 00 00 C0 FF 00 40 00 00 :®®€ß®€®®
In this case the drive is #8 so fef0-fef7 range is stable (mirrored 4 times from fee0).
If you can't see something similar it probably means that the TPI chip in the paddle is broken. These chips are hard to find as they were used in the 1551 only.
For the drive mechanics: 1551 has the same mechanics as the 1541C (normal 1541 will not do as it does not has the optical track 0 sensor)
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