Re: Commodore drives can be controlled on Apple II serial!

[dempson@actrix.gen.nz (David Empson)]

Supertimer <supertimer@aol.com> wrote:

> [posted to comp.sys.apple2 and emailed]
> 
> doug.cotton@cmdweb.com (Doug Cotton) wrote:
> 
> (discussion on getting the 1571 and CMD disk drives to run off the
> SmartPort)
> >Supertimer <supertimer@aol.com> wrote:
> >
> >>dempson@actrix.gen.nz (David Empson) wrote:
> >>>
> >>>SmartPort is serial, not parallel.  It also has several major
> >>>limitations: all data bytes transferred must have bit 7 set, and the
> >>>data rate is fixed (4 microseconds per bit cell, or 2 microseconds for
> >>>Apple 3.5 drives).
> >>> 
> >>>The only exception to this is the phase lines, which give you a four-bit
> >>>parallel output that can be controlled directly by software, and
> >>>probably the sense line, which gives you a one bit direct input.
> >> 
> >>So, based on what David wrote about the SmartPort, can it be used to
> >>emulate Commodore serial I/O?
> 
> I think that PH0 through PH3 must be the drive control lines that can
> be controlled through software.  Pins 1 through 3 are ground.  Pins
> 18 and 19 look like the serial input and output.

Pins 18 and 19 are the read and write data lines, which have the timing
and data format restrictions (4 microseconds per bit cell, bit 7 must be
set for reading, write must be every 32 microseconds exactly).

The only signals that can be controlled directly by the CPU are PH0-PH3
and the drive enable lines (only one enable line is active at a time).

Write Request is timed by and tied to the write sequence.  Write Protect
is the "sense" input.  It is used for write protect on a 5.25" drive, as
a general input for an Apple 3.5 drive.  From memory, there are
restrictions on when it can be sensed by software (based on the
read/write mode).

The SIDE1 signal you mention only applies to an Apple 3.5 drive, and is
only provided by the IIgs and IIc+.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand