Schematics for 7c81

Donno
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3 years 4 months ago #274177 by Donno

Replied by Donno on topic Schematics for 7c81

Thank You ! I will be ordering two 7I96S in the mean time just to get going and work on alternative board for the community

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3 years 4 months ago #274251 by Donno

Replied by Donno on topic Schematics for 7c81

Hi PCW just a quick one i want to replace PI5C16211/74CBT16211C with 2 x 74CBT3257 that should work, right ? and then on the schematics Q1/2/3 which PNP's do you use ?

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3 years 4 months ago #274253 by PCW

Replied by PCW on topic Schematics for 7c81

A 74CBT3257 would only handle 4 signals so you would need 4+ 74CBT3257s per port
PNP is a 2N4403

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3 years 4 months ago #274257 by Donno

Replied by Donno on topic Schematics for 7c81

You mean 2+ per port it is octal FET switch and there is 16 i/o

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3 years 4 months ago #274260 by PCW

Replied by PCW on topic Schematics for 7c81

Each "parallel port" connection has 17 signals
A 74CBT3257 only provides a signal path for 4 signals.
so 4+ 74CBT3257s would be needed per port (13 total)

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3 years 4 months ago #274261 by Donno

Replied by Donno on topic Schematics for 7c81

My apology i mean to write 74CBT3245

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3 years 4 months ago #274263 by PCW

Replied by PCW on topic Schematics for 7c81

That's better but a bit awkward because of the 17 bit wide ports

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3 years 4 months ago #274264 by Donno

Replied by Donno on topic Schematics for 7c81

IO0 to 16 = total of 17 per port. What is the function of the TOLA/TOLB and TOLC Pin ?

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3 years 4 months ago #274266 by Donno

Replied by Donno on topic Schematics for 7c81

Some update on my progress

Attachment not found

using EasyEDA with available components form JLCPCB and LCSC

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3 years 4 months ago #274269 by PCW

Replied by PCW on topic Schematics for 7c81

TOLX are the power to the bus switches, ~4.2V in 5V tolerant mode and
5V in 3.3V tolerant mode.

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