topic Re: sharing SCI port in S12 / MagniV Microcontrollers

sharing SCI port

fadi — Thu, 04 May 2006 02:51:53 GMT

Hello all,

is a chip that i can youe to multiplex the SCI port between 2 connections. the idea is that i'm using the SCI port to communicate to an mc33290 chip and i need it also to communicate with the PC through RS232. i'm using the 9s12c32(44pin) that comes with the studen learning kit and it has only one SCI port.

Thank you all.

Re: sharing SCI port

fadi — Thu, 04 May 2006 11:23:42 GMT

"is there a chip that i can use to multiplex the SCI port between "

Re: sharing SCI port

peg — Thu, 04 May 2006 11:56:49 GMT

Hi fadi,

How about using a 74HC125A

Regards Peg

Re: sharing SCI port

fadi — Thu, 04 May 2006 13:48:59 GMT

is the 74125 capable of passing the signal both ways on the same pin ? i thought each transmission is from Ax->Yx . i was thinking maybe there is an IC that can do this on a single pin instead of having to control the pins for each RX and TX.

Thank you

Re: sharing SCI port

peg — Thu, 04 May 2006 14:08:31 GMT

No it is not possible.

But aren't you going to multiplex the signals at the mcu level where they are unidirectional? one Tx output and 1 Rx input.

Otherwise please explain.

Regards Peg

Re: sharing SCI port

fadi — Thu, 04 May 2006 14:22:28 GMT

yes thank you it sliped my mind .
i was thinking of bidirectional data on a single line , dunno why

Thank you again.

so this post would not be a wast for the people who want bidirecitonal data flow, search on google for "Dual Bus Switch".

am i allowed to post links to device pages from other manufacturers?

Thank you all.

Re: sharing SCI port - Link to other manufacturers

Alban — Fri, 05 May 2006 16:30:43 GMT

Yes Fadi, you are !
Anything that helps can be posted...
However, don't praise the competition too much
Cheers,
Alban.

Re: sharing SCI port

fausto — Thu, 18 May 2006 05:41:13 GMT

Hello,

Hey Peg, I have the same problem fadi was going through, I saw you suggested 74HC125A , the problem is that this part seems to be under " no longer manufactured", do you know other chip that help on multiplexing the SCI port?

Thanks

Fausto

Re: sharing SCI port

fadi — Thu, 18 May 2006 13:28:02 GMT

Hi fausto, look for a tristate buffer this is what the 74*125 is.
But i don't understand 74HC125A is no ore produced. i think they have millions of it in electronics shops .

anyway these are bidirectional buffers, an overkill but maybe:
http://focus.ti.com/docs/prod/folders/print/sn74cb3t3306.html

Good luck

Re: sharing SCI port

peg — Thu, 18 May 2006 17:44:45 GMT

Hi,

The term " non-inverting" should also be added to your spec.

Maybe you are being fooled into thinking they are being discontinued by the Pb-free thing. Check to see if a lead-free version is available (usually with an extra letter or a "+" or something). Otherwise the octal types probably will have a longer life. HC241 actually helps by having 4 active high enabled and 4 active low (only one pin on your mcu) or maybe HC541 or HC244? But you only need half the package.

Regards Peg

Re: sharing SCI port

bigmac — Thu, 18 May 2006 19:43:28 GMT

Hello all,

Another multiplexing device for consideration is the 74HC4053. This is actually a 2-way analog multiplexer, with three independent sections. It works satisfactorily for digital signals, and being an analog multiplexer, it is bi-directional.

Regards,
Mac