Re: 6809 assembly knowledge needed

From: Jim Brain <>
Date: Thu, 04 Feb 2010 18:25:23 -0600
Message-ID: <>
On 2/4/2010 12:52 PM, Nate Lawson wrote:
> Rainer Buchty wrote:
>> On Wed, 3 Feb 2010, wrote:
>>> - The PDF says: "I/Os are not 5V tolerant". I see a lot of resistors
>>> to handle this. But is it still capable of driving the C64 plus some
>>> extras? If not, what is needed to make it capable? For example, will
>>> 74HCT245's and 541's do?
>> You don't need extra level shifters as GODIL comes readily equipped with
>> such. These you can use (adds 700ps to the timing path), but you don't
>> need to in case you don't require 5V tolerance.
> Right, and you can configure the board for either the level shifter or
> series resistors.
How do you do the selection?  I can see turning off the level shifters 
by deselecting the 16211 bus transceivers, but how do you turn on series 
resistors?  Are they just always populated in parallel with the bus drivers?

I ask because I am working on a C64/128 expansion port (think CMD EX3 or 
FB-EX3, etc.).  I've been asked to put some bus drivers on the board to 
clean up the C64 bus.  SOme other designs are using '541s and 245s, but 
those have way too long of latency.  The 16211 looked interesting 
because it only has a tiny < 1ns latency, but I would prefer a way to 
deselect it if someone finds carts that do not like it.


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Received on 2010-02-05 01:00:04

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