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Re: [N8VEM-S100:873] 1.1k 10-pin Resister Pack supplier (or alternative values)?
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- Subject: Re: [N8VEM-S100:873] 1.1k 10-pin Resister Pack supplier (or alternative values)?
- From: Paul Birkel <pbi...@gmail.com>
- Date: Thu, 21 Jun 2012 01:36:39 -0400
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Thanks Tom, John. Doing the verification part here before the testing
:->. We need to collect these sorts of "tweaks that work" for the
various boards in appropriate locations methinks.
John: While I've been reading up on the various calculations
regarding the selection of o.c. pullups and fanout/in calculations
(Wilcox Section 3.1.1 is quite good) I haven't found anything specific
on the selection of open-input pullups. Recommendations?
On Wed, Jun 20, 2012 at 11:38 PM, John Monahan <mon...@vitasoft.org> wrote:
> Paul this question has come up before. There is nothing special about the
> 1.1K value of the pull-up resistors for the TTL circuits. 1K will be fine,
> as would the more common 1.2K types. Jameco used to sell 1.1K's but no
> longer do. The choice of value for pull-ups like that is a balance between
> noise immunity (low values, ~1K) to power utilization (high values ~2K or
> even 4.7K). Other factors are signal pulse width and fan-out.
> From: John Monahan Ph.D
> e-mail: mon...@vitasoft.org
> Text: mon...@txt.att.net
> -----Original Message-----
> From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On
> Behalf Of Paul Birkel
> Sent: Tuesday, June 19, 2012 10:32 PM
> To: n8vem...@googlegroups.com
> Subject: [N8VEM-S100:870] 1.1k 10-pin Resister Pack supplier (or alternative
> The S-100 MSDOS Board, Z80A Master CPU Board, and Serial I/O Board all
> specify the use of a 1.1k 10-pin Resister Pack.
> This seems to be an uncommon part. Is there a recommended supplier?
> Alternatively, is the value critical in these three board-uses?
> The S-100 MS-DOS Board uses a pair of packs (RR7/8) as input pull-up
> resistors on the two 74LS165 address decoders. The Z80A Master CPU Board
> similarly uses three packs (RR3/4/7) as input pull-up resistors on its three
> 74LS165 address decoders. It seems to me that in this use the values are
> fairly non-critical. What is the recommended, commonly-available,
> alternative resistor value?
> The Serial I/O Board is a bit more complicated. It uses a single pack
> (RR1) which connects to PU1K-A thru PU1K-I.
> 1. PU1K-A/B/C are used on the Z8530 UART_INT*, UART_IEI, and UART_INTA,
> apparently as input pull-ups.
> 2. PU1K-E/F are used as pull-ups on two outputs of a open-collector
> 74LS06N (the other 4 outputs are spares).
> 3. The remaining 4 pack-resistors are spared.
> Given this mixed-use, what would be the recommended, commonly-available,
> alternative resistor value? Or should I consider hand-wiring single
> resistors in each case -- and then what would be the recommended values in
> each case (UART input pullups; o.c.