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

[doug.cotton@cmdweb.com (Doug Cotton)]

In article <1d6d3kr.1v70ywl127dfoiN@dempson.actrix.gen.nz>,
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.

That last bit is interesting... standard Commodore serial I/O only uses
three lines... ATN (Attention), CLK (Clock) and DATA (Serial Data). The
other three lines on the bus are a ground, reset and SRQ (Service Request).
The latter is needed for fast serial only, though schemes like JiffyDOS
perform (sometimes outperform) fast serial without even using this line.

-- 
Doug Cotton <doug.cotton@cmdweb.com>

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