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AltairZ80: mfdc: allow disk controller to work with MZOS disk images

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Do not insert the computed checksum for VGI disk images, since the
checksum is already present in the sector data.
This commit is contained in:
Mike Douglas 2015-03-18 19:10:07 -07:00 • committed by Howard M. Harte
parent 590895bfe5
commit 89a3783281
1 changed files with 8 additions and 1 deletions
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9
AltairZ80/mfdc.c
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@ -499,7 +499,14 @@ static uint8 MFDC_Read(const uint32 Addr)
checksum = adc(checksum, sdata.raw[i]);
}
sdata.u.checksum = checksum & 0xFF;
#ifndef USE_VGI
/* VGI has the checksum in the data read from the disk image,
* so inserting the computed version of the checksum is not
* necessary. MZOS computes the checksum differently than all
* other VG software, so this allows MZOS disks to work
*/
sdata.u.checksum = checksum & 0xFF;
#endif
/* DBG_PRINT(("Checksum=%x" NLP, sdata.u.checksum)); */
mfdc_info->read_in_progress = TRUE;
}