Settle delay and other timings, three-mode drives
Settle delay

How is the drive settle delay handled? That's the delay needed after moving the heads to the desired track, before reading/writing data. Do programs which access the SCP have to handle that themselves, or does the hardware/firmware guarantee it for the step to track command?

The doc for command 0x91 set parameters says "Word 4 - delay (in milliseconds) after seeking track 0 (default 15)". Which suggests the SCP only uses a settle delay after stepping to track 0 via command 0x88 - seek track 0. Should user programs wait after issuing command 0x89 step to track, before reading data? And similarly wait after issuing commands 0x8A and 0x8B (step inwards and outwards)?

The Citizen Z1DA-78A floppy drive specification at
mentions 18ms being needed as the settle delay. My drive is a Citizen Z1DE-57Bb (HP OEM model) and I'm having problems getting good dumps using it. I'll post about that in another thread.

Three-mode floppy drives

When using a three-mode floppy drive (i.e. one capable of being told to spin at 360rpm instead of 300rpm), can the SuperCard control the drive mode? I notice the 0xA0 read flux data command has bit 3 related to that. Does that flag just tell the SCP to read at a higher resolution, or does it tell the drive to spin at that speed?

Various drive manuals say the mode (for HD disks at least) is selected by the state of drive connector pin 2.
According to "SAMSUNG-SFD321B-070103.pdf"
the mode is set by the density select line (pin 2 of the 34-pin connector):
 - HD disk and DS line HIGH: 2.0MB (normal 300rpm)
 - HD disk and DS line low: 1.6MB (360rpm)
 - DD disk: always 1.0MB regardless of DS line (300rpm)

According to "FDAA-522041_YD-702D-6639D_3.5_Floppy.pdf"
those Y-E Data drives can be jumpered for both senses of pin 2 (the Y-E Data PDF calls that line MODE SELECT). In other words, either the same as SFD-321B, or the opposite: HD disk and pin 2 low: 2.0MB/300rpm, HD disk and pin 2 high: 1.6MB/360rpm. If I read the PDF correctly, it looks like that particular Y-E Data drive ships with jumpers set to the opposite of the SFD-321B.

Teac also made 3-mode floppy drives (FD-235HG). According to "Teac FD-235HG manual.pdf"
(document page 22, PDF page 25)
MODE SELECT LOW: 1.6MB (360rpm), MODE SELECT HIGH: 2.0MB (300rpm)
So Teac 3-mode selection is same as Samsung.

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Settle delay and other timings, three-mode drives - by mark_k - 11-14-2016, 10:15 AM

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