Re: [N8VEM-S100:659] Re: 6502 board resistor networks

[Mike <mi...@pikeaero.com>]

Guys,

Generally at the kind of bus speeds we're dealing with here, there is a
fair bit of leeway regarding slew rate (rise and fall times). I just
wanted to point out that the strength of pull-up resistors has an effect
on the slew rate of the signal being pulled up. Thus a signal with a 1K
resistor will rise faster than the same signal with a 4.7K resistor.

So there are trade offs, like everything else, just thought I'd point
that out.

--Mike


On 01/12/2012 02:04 AM, John Monahan wrote:
> In generally 1k is sufficient for TTL Pullups. The reason for higher values is to save power drain on the v regulator. You can go up to about 4.7k
> Pullups to bus lines are another story
> Joh
> 
> Sent from my iPhone
> 
> On Jan 11, 2012, at 7:12 PM, yoda <yo...@r2d2.org> wrote:
> 
>> Hi Andrew
>>
>> Would it be possible to have some design rules in general.  I have
>> seen a lot of these boards use parts that are not easily obtainable
>> which suggests these are copies of old boards without thought.  If
>> they are supposed to be pull-up resistors then in general I would
>> expect 1K or 4.7K be specified as they are pretty standard.  I checked
>> Jameco, Digikey and Mouser and they don't have 1.3 K.  I know
>> experienced people can interpret schematics but it tends to discourage
>> new people into the hobby that don't have that experience.  Also it
>> would be nice to do some standardization of buss interface.  I see
>> this board uses ls541's where most other boards use ls373's so one has
>> to "stock" many more parts to participate.
>>
>> Just a thought
>>
>> Dave
>>
>> On Jan 11, 6:50 pm, "Andrew Lynch" <LYN...@YAHOO.COM> wrote:
>>> Hi Kipp!  The 1.3K ohm resistors are all pull up resistors and have a broad
>>> tolerance.
>>>
>>> Almost certainly the 1.2K ohm resistors will work just fine.
>>>
>>> Thanks and have a nice day!
>>>
>>> Andrew Lynch
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>> -----Original Message-----
>>>> From: n8vem...@googlegroups.com [mailto:n8vem-
>>>> s1...@googlegroups.com] On Behalf Of kyeakel
>>>> Sent: Wednesday, January 11, 2012 10:44 AM
>>>> To: N8VEM-S100
>>>> Subject: [N8VEM-S100:655] 6502 board resistor networks
>>>
>>>> I couldn't find 1.3k ohm resistor networks. I have 1.2k networks, any
>>> issue
>>>> with using them?
>>>> Kipp
>>