[time-nuts] Electronics Question

[lists at lazygranch.com]

I don't follow exactly what you are doing here, but 232 receivers are generally TTL compatible. Connecting 232 outputs to logic can't be done. The signal swing is too large, and worse yet, goes negative. You can scale it with resistors and use a diode clamp (Schottky). 

As a side note, these 232 chips have jitter in both the receive and transmit path. The charge pump gets into the rest of the chip. The jitter is generally an inside specification. I never saw anyone publish it. The manufacturer needs to know the jitter to set up limits in the test program.
 
-----Original Message-----
From: "Jason Rabel" <jason at extremeoverclocking.com>
Sender: time-nuts-bounces at febo.com
Date: Wed, 27 Jul 2011 15:48:19 
To: <time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: [time-nuts] Electronics Question

This is only pseudo time-nuts related...

I'm wiring up (yet another) net4501 with a Motorola M12 GPS..

This net4501 has the RS232 driver chip there for the 2nd serial port (previous units I purchased didn't, which made life easier for
me).

Can I solder my GPS tx/rx lines on the ttl side of the RS232 chip and will it work? Or will the rs232 chip hold the voltages
low/high because there is no signal on the input sides?

This is just kind of "for future reference" question. I half wasn't sure if it would work, and half didn't care to try and solder a
wire to a TSOP lead. So I bought a Max3222 PDIP and can make a proper interface. The prototype board will also give me room for some
extra LEDs. ;)

This is kind of an experiment to see how a regular M12 compares to the M12+T for NTP purposes. I'll probably build a fresh NanoBSD
image because I need to modify a line of code in NTPns to remove a TRAIM command that makes the regular M12 PPS stop. I also want to
build the latest regular NTP distro.



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