[N8VEM: 16455] Warning on using W65C22S VIAs on the 6x0x IO mezzanine board

[Ian May]

The "My understanding of the N8VEM 6x0x boards" v2(1).doc document on the
wiki under the "Obtaining the parts" section on the mezzanine board on page
10 states "The 6522 is also available new from Mouser etc. Buy the ‘S’
(Standard CMOS) version".

One of the key differences between the W65C22S and W65C22N is the circuitry
connected to the IRQ pin. The W65C22N has an open drain output like all the
previous NMOS and CMOS parts and it can be wire ORed with the IRQ pins of
other devices. The W65C22S has a standard totem pole output, so in a wire
ORed system if another device attempts to pull the IRQ line low there will
be a short across the 5V supply between the pull-up transistor in the W65C22S
and the device pulling the line low. If you wish to use the W65C22S in a
wire Ored system the data sheet suggests using "a low voltage diode (<0.5V)
in series with the W65C22S totem pole IRQB output." See page 31 of the
W65C22 data sheet.

The correct device to use with the mezzanine board is the W65C22N.

Cheers,
Ian.

[oscarv]

Ian,

Whoah - that's an important bludner in that text (which I wrote).

The document then actually needs two updates since it was written: (a) how
to use the new version of the 65c02, something that was discussed earlier
this year, and (b) this related, rather important correction on the 62c22.

Can anyone tell me how I can change a document stored in the N8VEM
repository? I did not post it myself there and I'm a bit clueless on how to
get write access.

Kind regards,

Oscar.

[oscarv]

For the record, I corrected the "My understanding of the 6809..." document,
new version is here (link)<http://n8vem-sbc.pbworks.com/w/file/70801568/My%20understanding%20of%20the%20N8VEM%206x0x%20boards%20v2.1.doc>
.
Thanks!

Oscar.

[AG5AT]

Oscar,
You may want to go back and clearly state that for a W65C02S6TPG-14,
placing a jumper from pin 1 JP2 to pin 1 JP3 is necessary in addition to
your information.

Aug

Post by oscarv
For the record, I corrected the "My understanding of the 6809..."
document, new version is here (link)<http://n8vem-sbc.pbworks.com/w/file/70801568/My%20understanding%20of%20the%20N8VEM%206x0x%20boards%20v2.1.doc>
.
Thanks!
Oscar.

[oscarv]

[Andrew Lynch]

Hi Oscar! Thanks ! You have an account on the wiki and are a writer. I
can upgrade you to an editor if necessary or post what changes you need
done. Thanks and have a nice day!

Andrew Lynch



From: n8vem-/***@public.gmane.org [mailto:n8vem-/***@public.gmane.org] On Behalf Of
oscarv
Sent: Monday, November 04, 2013 9:57 AM
To: n8vem-/***@public.gmane.org
Subject: [N8VEM: 16459] Re: Warning on using W65C22S VIAs on the 6x0x IO
mezzanine board



Ian,

Whoah - that's an important bludner in that text (which I wrote).

The document then actually needs two updates since it was written: (a) how
to use the new version of the 65c02, something that was discussed earlier
this year, and (b) this related, rather important correction on the 62c22.

Can anyone tell me how I can change a document stored in the N8VEM
repository? I did not post it myself there and I'm a bit clueless on how to
get write access.

Kind regards,

Oscar.
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[Andrew Lynch]

Hi

Is there a small simple change to the design we need to do to resolve this
or is it a documentation issue?



If there is a change needed what is it specifically.



Thanks and have a nice day!

Andrew Lynch



From: n8vem-/***@public.gmane.org [mailto:n8vem-/***@public.gmane.org] On Behalf Of
Ian May
Sent: Sunday, November 03, 2013 8:20 AM
To: n8vem-/***@public.gmane.org
Subject: [N8VEM: 16455] Warning on using W65C22S VIAs on the 6x0x IO
mezzanine board



The "My understanding of the N8VEM 6x0x boards" v2(1).doc document on the
wiki under the "Obtaining the parts" section on the mezzanine board on page
10 states "The 6522 is also available new from Mouser etc. Buy the 'S'
(Standard CMOS) version".

One of the key differences between the W65C22S and W65C22N is the circuitry
connected to the IRQ pin. The W65C22N has an open drain output like all the
previous NMOS and CMOS parts and it can be wire ORed with the IRQ pins of
other devices. The W65C22S has a standard totem pole output, so in a wire
ORed system if another device attempts to pull the IRQ line low there will
be a short across the 5V supply between the pull-up transistor in the
The correct device to use with the mezzanine board is the W65C22N.

Cheers,

Ian.
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[oscarv]

Andrew,

Post by Andrew Lynch
Is there a small simple change to the design we need to do to resolve
this or is it a documentation issue?

A documentation issue really;

If there is a change needed what is it specifically.
When using a new-production-run 6502 (W65C02S6TPG-14) the builder needs to
pull pin BE on the processor high.

When using a new-production-run 6522, do not buy the W65C22S but rather
the W65C22N.

Regards,

Oscar.