Z80 home brew with FDC

[Alexis]

On Sun, 21 Sep 2008 10:42:46 pm Andrew Lynch wrote:
> Hi Alexis, Rich,
>
> As for the data separator, I am using an FDC9229 although you could use a
> FDC9239 I think.  The chips are still available but not exactly common. 
> You have to look but you can find them.  I have some pointers if you'd
> like.

I'd like to see if the data separator on the FDC-1 for the SYM-1 would work on 
the 765. The FDC-1 uses a FD179x controller and it appears it uses the same 
data clock and raw data inputs as the 765. I've built the FDC-1 for my SYM-1 
last week and it works a treat, in both FM and MFM modes and on 720k 3.5" 
disks. I used an SMC FDC1797 from an old word processor. The board it came 
off had a 9229 on it so I think there's a good chance the circuit will work.

The decoder is made up of a 74LS197 (clock divider), a dual 74LS74 flip-flop, 
both used, a 74LS163 counter and an inverter. There are also some open 
collector NAND gates to select the clock rate for either 8" or 5.25" drives. 
It'll use more individual IC packages, but they're *much* easier to find.

The circuits are, of course, at 6502.org:

http://6502.org/users/dallas/SYM/SYMDOS2/fdc_sheet1.pdf
http://6502.org/users/dallas/SYM/SYMDOS2/fdc_sheet2.pdf

Thanks for that link to the SMC datasheet too. I'll give it a good looking 
over when it's downloaded. I was never 100% clear on the format procedure 
given in the Intel datasheet, so hopefully the SMC one will be a little 
better!

Thanks,

Alexis.