CMB1ABA serial port specs

[David_Ashman]

I'm having difficulty finding the I/O specifications for the serial ports on the CMB1ABA Rugged Board Element.  Does anyone know if they are RS232 compliant, or are they just simple 5v or 3.3v TTL level I/O?  Thanks!

[n_scott_pearson]

AFAIK, the ZT3243E RS232 transceivers are configured for 3.3v CMOS I/O.

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[David_Ashman]

@n_scott_pearson are you saying that the ZT3243E IC is used on the CMB1ABA Rugged Board Element?  If so, thank you - that answers my question. 

If not, there are many ICs out there that operate from 3.3v VCC and use charge pumps to generate the +/-5 to 7v required to comply to RS232 comm standard.  My question is: what voltage levels are transmitted out of and received in to the CMB1ABA serial port from the outside world?  Does the serial port generate RS232 (+/-5 to 7v) level signals, or is it simply a TTL 3.3v or 5v interface.

[n_scott_pearson]

No, not positive, but this is device that was identified for other NUCs. I have asked for clarification, but the folks that can answer are off for their weekend. I will let you know, hopefully Monday.
A 3.3V CMOS process will use 3.3V (>2.4V (at output), >2V (at input)) for logic 1 and 0V (<0.55V(at output), <0.8V (at input)) for logic 0.
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[n_scott_pearson]

Development team responded. The ZT3243 Part on the CMB1ABA Element board is specifically the ZT3243LFEY (if that matters). They also confirmed it is using 3.3V CMOS process.

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[David_Ashman]

Thank you very much @n_scott_pearson.  To summarize the answer and close out the thread, the Serial Ports on the CMB1ABA Rugged Board Element utilize the Zywyn ZT3243LFEY RS232 driver.  Which means the 9 pin serial port header I/O shown in Table 8 of the Product Specification is at RS232 voltage levels.  Additionally, the VCC pin of the ZT3243LFEY is 3.3v. 

[n_scott_pearson]

If, by 'RS232 voltage levels', you mean 3.3V for logic 1, 0.5V for logic 0, then yes.

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[David_Ashman]

Hi @n_scott_pearson I'm thinking that we're missing each other's point.... let me try to explain my side.  The Zywyn ZT3243LFEY located on the CMB1ABA Rugged Board Element is also known as a TTL to RS232 "bridge" or "translator".  In this case, the Intel processor communicates to the ZT3243LFEY via TTL tx pin which then "translates" the signal to RS232 voltage levels to talk to an external device attached to the serial port.  That external device can also talk back to the Intel processor via RS232 voltage levels to the ZT3243LFEY which "translates" the signal back to TTL rx pin to the Intel processor. 

From Wikipedia: "The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels for the data transmission and the control signal lines. Valid signals are either in the range of +3 to +15 volts or the range −3 to −15 volts with respect to the "Common Ground" (GND) pin; consequently, the range between −3 to +3 volts is not a valid RS-232 level."

Respectfully, I don't agree with your statement that "3.3V for logic 1, 0.5V for logic 0" is RS232 and is valid I/O voltage levels for the 9 pin serial port header I/O shown in Table 8 of the Product Specification.

What am I missing?

[n_scott_pearson]

Look at this search and summary: https://www.google.com/search?q=rs232+cmos+level&oq=rs232&aqs=chrome.2.69i57j69i60j69i59l2.3098j0j7&client=ms-android-att-us&sourceid=chrome-mobile&ie=UTF-8#sbfbu=1&pi=rs232%20cmos%20level
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