On 30 May 2019 at 20:40, Roger Burrows wrote:
On 30 May 2019 at 22:15, Christian Zietz wrote:
Nicolas Pomarède schrieb:
Seeing Roger's test on his TT, where bit 4 was always 0 (ie inserted) it
seems though that not all TT had a compatible drive with such pin 34.
If Roger tested while the drive was *not* selected (via the bit in the
YM2149 register), even with a drive that supports that signal he would
have always gotten a 0. This is because, as mentioned, the drive only
sets this line (and therefore the bit to 1) when it's selected. At least
my drive does.
I will retest, making sure the drive is selected. I probably need to write a
test program first ...
OK, I've done this, and can confirm Christian's report: after a diskette is
inserted, if the drive is selected and a floppy read is done, 0xfffa81 contains
0x7f. This value persists until a read of a different track is done, at which
point 0xfffa81 contains 0x6f. Note: just switching to the other side of the
original track read does NOT alter the contents of 0xfffa81.
This applies to both my TTs.