Re: Handic VIC-Switch

From: Jim Brain <brain_at_jbrain.com>
Date: Thu, 2 Nov 2017 12:49:34 -0500
Message-ID: <21ba4af4-4e8e-845b-68c1-ae774333eb93@jbrain.com>
On 11/2/2017 9:52 AM, Mia Magnusson wrote:
>
> Is there really more than sending 8 clock pulses and drive the data
> line? Of course with the correct polarity of all stuff e.t.c.
It's less a about when to send the $ff. and more about when *NOT* to.

And, sending the $ff is trivial.  It's watching for the $ff indicator on 
the computer side * 8 ports at the correct time, and then ignoring other 
$ff signals at any other time.

Again, it's not insurmountable, but you either need to build 8 sets of 
TTL logic to correctly watch for the indicator on the 8 incoming ports 
(and ignore any other time), you need to use a microntroller that can 
watch the 8 CLK lines at the correct time, or you need to implement the 
functionality in a PAL/GAL/CPLD.  I found that a 16MHz uC could not 
satisfactorily watch the CLK lines for activity, and I had no desire to 
bulk up on TTL in the board, so I decided to learn Verilog so I could 
implement the required functionality.

JIm




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Received on 2017-11-02 18:00:03

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