MITS 2SIO serial chip?

From: Ben Franchuk <>
Date: Sun Dec 16 18:27:25 2001

Richard Erlacher wrote:
> Why? The WD37C65 is a much easier part to use, and it programs pretty much like
> a NEC uPD765, drives the cable directly, and automatically deals with the
> data/clock separation for 500 KHz, 250 KHz, and 125 KHz data rates at both 300
> and 360 rpm. You can lift 'em from broken HDC's or order 'em from
> (Rochester Electronics). They're most common in PLCC-44, which
> you should be able to handle, even if, like me, you didn't listen to Mom when
> she told you to stop that.

It sounds like a nice chip. Since all I have is 3 1/2" 1.44mb drives I
have a fixed 500 Khz clock, thus less programing. Also the chips are
if you can find them $7.25 _at_ BG micro. I was looking some nec? chips at
and they were over $75 each.

  If you must use a WD part, which I prefer also, then
> use a WD179x with a FDC9229. That does everything in two chips, including
> selecting the appropriate clocks. The 2797 uses an analog PLL and, unless you
> are satisfied with a single data rate, that means multiple filters and analog
> muxes, etc.

Thanks for the info. While a 2 Mhz machine would have been the speed of
system in the 80's I might as well go to 4 Mhz since the FPGA will run
that fast.
As a side note a 2 Mhz machine is about the same speed as a PDP-8. 1.5us
for a jump.
2.5 us for memory access.
Ben Franchuk --- Pre-historic Cpu's --
Received on Sun Dec 16 2001 - 18:27:25 GMT

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