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

[supertimer@aol.com (Supertimer)]

[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?
>
>It sounds like it at this point. Due to the limited number of lines, I'd
>say use them for ATN, CLK, DATA and SRQ. RESET could be done in the 'cable'
>with a one-shot, or could be ignored for that matter... isn't an absolute
>necessity, though it would be better to have it than not. Is there by any
>chance some form of a reset signal on this port already? That would be
>another option. Need to pick up a ground too, but hopefully the port has
>that. Is there any documentation on this port anywhere?

Doug, here is a schematic of the SmartPort.  Hopefully, this will help
in making an interface cable to the 1571 and CMD drives!

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.

Diagram of the DB19 SmartPort of the Apple II --
(it is a daisychain floppy serial port)



10    9    8    7    6    5    4    3    2    1
   19   18   17   16   15   14   13   12   11




1. ground
2. ground
3. ground
4. reserved
5. -12 volt
6. +5 volt
7. +l2 volt
8. +l2 volt
9. ENABI - actlve low when
           first drive is accessed
10. WPROT - write protect
11. PH0 - drive control
12. PH1 - drive control
13. PH2 - drive control
14. PH3 - drive control
15. WREQ - active low when write
           to drive is required
16. SIDE 1 - active high when side
             1 of diskette is accessed
17. ENAB2 - active low when
            second drive is accessed
18. RDATA - drive data input to computer
19. WDATA - drive data output from computer