Thanks, dq. I have seen that doc, but it speaks mainly of the
3.5 drive, which had several enhancements not available on the
5.25 drive. Was the Apple ][ controller sufficiently similar to
the IIgs and progeny that this documentation is appropriate for
it also? I've never heard the Apple ][ controller chip referred
to as 'IWM' -- is that my ignorance, or was the chip renamed, or
are they (maybe slightly) different beasts?
- Sean
Douglas Quebbeman wrote:
>
> > Until I get my hands on a copy of the venerable "Beneath Apple Dos"
> > is there anyone who can point me to an online resource describing the
> > Apple ][ disk controller P6 ROM state machine? The exact uses
> > for the Q6 and Q7 switches ($C0EC-$C0EF)? Or would be willing to
> > summarize from the mighty tome for me?
>
> From:
> http://www.mac.linux-m68k.org/devel/iwm.php
>
> : =======================
> : Accessing IWM Registers
> : =======================
> : The IWM chip has several internal registers available to programs.
> : Access to these registers is controlled by the Q6 and Q7 switches.
> :
> : +=====+=====+=======================================+
> : | Q6 | Q7 | Register |
> : +=====+=====+=======================================+
> : | off | off | Read data register |
> : +-----+-----+---------------------------------------+
> : | off | on | Read handshake register |
> : +-----+-----+---------------------------------------+
> : | on | off | Read status register |
> : +-----+-----+---------------------------------------+
> : | on | on | Write mode register (if drive is off) |
> : | | | data register (if drive is on) |
> : +-----+-----+---------------------------------------+
> :
> : The mode register is a write-only register containing several flag bits
> : which control various features if the IWM. To access it, turn off the
> : drive (by accessing ENABLE), turn on Q6 and Q7, and write to any
> : odd-numbered address in the $C0E0...$C0EF range.
>
> hth,
> -dq
Received on Wed Sep 05 2001 - 17:36:25 BST