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Re: [N8VEM-S100:1536] Z80 CPU board part issue

Hi Pete,
  As others have noted, the 1K sips with be fine but I had the same question last year so I asked the hardware designer John Monahan on the S100computers.com website hardware forum and below are the details.  I couldn't figure how to link directly so I copied/edited/pasted the important details.


Unregistered user (Guest) Username:            Posted on Tuesday, May 08, 2012 - 9:49 am:             


 Hi John & All, I've got my blank z80 PCB with me and have looked at the schematics & have a quick question regarding the use of 1.1k resistor SIPs for RR2, RR3 & RR4. It looks like a simple pull up for the inputs to the shift register so I am wondering why 1.1k and not 1k. The reason I am asking is I have lots of 1K SIPs but no 1.1K SIPs and the 1.1K SIPS seemed to be harder to find. I assume there is a reason these were chosen so I wanted to find out the reason.
Thanks, Jeff Galinat


John Monahan  Posted on Tuesday, May 08, 2012 - 9:51 pm: 


 Hi Jeff, definitely you can use 1K's. There seems to be some tradition going way back as to what pull-up’s should be. I've seen 1K, 1.1K, 1.2K even 2K and 5K. You are balancing noise immunity against total board power needed


Jeff Galinat (Jgaliant)             Posted on Thursday, May 10, 2012 - 1:49 am


 Hi John, I forgot to add in my last post that 1K SIPs are used as pullups at RR5, RR6, RR8 and RR9 & since 1Ks can also be used at RR2, RR3 & RR4, the BOM/parts list could be simplified to all 1k SIPS except for RR7 which is 4.7k.


On 4/7/2013 2:20 AM, Pete Plank wrote:

I'm trying to put together the Z80 CPU board and ran into an issue regarding the 1.1K bussed resistor networks -- I can't find them in stock anywhere (eBay, Mouser, Digikey, etc.). I believe a compatible part number is Bourns 4610X-101-112. I need 3 of these -- anyone know of a source or have some extra they'd be willing to sell?

Thanks much,

Pete Plank