2nd User port for Beeb?

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MartinB
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Re: 2nd User port for Beeb?

Post by MartinB » Mon Jul 16, 2018 2:31 pm

I did indeed design BeebSID to fit in to an already very congested and contested page $FC but it significantly pre-dates the second user port and the latter technically conflicts with existing legacy usage but there always has to be pragmatic thinking and compromise with these things.


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Last edited by MartinB on Mon Jul 16, 2018 2:31 pm, edited 2 times in total.

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Elminster
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Re: 2nd User port for Beeb?

Post by Elminster » Mon Jul 16, 2018 2:33 pm

MartinB wrote:
Mon Jul 16, 2018 2:31 pm
but it significantly pre-dates the second user port and the latter technically conflicts
Or, more likely, you are a time lord.

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1024MAK
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Re: 2nd User port for Beeb?

Post by 1024MAK » Mon Jul 16, 2018 2:54 pm

It's possible to use a 74LS138 (or a 74HCT138) in place of the 74LS42 in position IC4, but the pin-outs are different.

Mark

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sweh
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Re: 2nd User port for Beeb?

Post by sweh » Mon Jul 16, 2018 3:36 pm

MartinB wrote:
Mon Jul 16, 2018 2:31 pm
I did indeed design BeebSID to fit in to an already very congested and contested page $FC but it significantly pre-dates the second user port and the latter technically conflicts with existing legacy usage but there always has to be pragmatic thinking and compromise with these things.
Yeah, I just took the original design, which allowed for selectable addresses, just because that space is so crowded. The HostFS:UPURS code I wrote for it will work with whatever base address you select; just update the few defines to point to the relevant ports.

But "works for me" was the primary goal :-)
Rgds
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tricky
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Re: 2nd User port for Beeb?

Post by tricky » Mon Jul 16, 2018 4:08 pm

Don't know if this is still useful!
sydney wrote:
Sun Sep 29, 2013 4:59 am
It's a bit early and I've woken after dreaming what I'm about to write so forgive me if it's nonsense!
Would it be possible to change the pins on the user port used by UPURS or MMBEEB so that they don't clash as they do at present and have them both work off one user port?
MMBEEB uses GND,CB1,CB2,PB0,PB1,+5V
UPURS uses GND,PB6,PB7,PB1,PB0
If we changed MMBEEB to PB2 and PB3 and changed the software could both be used at the same time from one user port?
Duikkie's SmartSPI will work with any even pair of PB lines without any software changes.
I use PB4/5 on a couple of my beebs with solidisk sideways RAM which uses PB0/1/2 to select the SWR bank to write to.

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Elminster
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Re: 2nd User port for Beeb?

Post by Elminster » Mon Jul 16, 2018 4:59 pm

Not for me as I don’t use Mmc, but might for others.

I was more interested in using upurs and leaving main user port free. The other extra user is just a bonus.

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Re: 2nd User port for Beeb?

Post by Elminster » Mon Jul 16, 2018 4:59 pm

1024MAK wrote:
Mon Jul 16, 2018 2:54 pm
It's possible to use a 74LS138 (or a 74HCT138) in place of the 74LS42 in position IC4, but the pin-outs are different.

Mark
Pretty sure I have some of those. I may not need to buy anything then. Just find some time.

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1024MAK
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Re: 2nd User port for Beeb?

Post by 1024MAK » Fri Jul 20, 2018 10:55 pm

Extra user ports using 74LS138.jpeg
Extra user ports using an 74LS138 in IC4 position.
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Elminster
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Re: 2nd User port for Beeb?

Post by Elminster » Fri Jul 20, 2018 11:21 pm

Thanks. Need to double check but i think I already have parts for all of these.

Edit: Think I need to give the original article a proper read.
Last edited by Elminster on Sat Jul 21, 2018 2:01 am, edited 1 time in total.

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