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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics
Subject: Re: Using MC1488 for TTL->RS-232
Summary: Try using the correct power supply voltages...
Message-ID: <3583@kitty.UUCP>
Date: 1 Jan 90 00:34:32 GMT
References: <MZb4w2600WB88M=4wv@andrew.cmu.edu>
Organization: Recognition Research Corp., Clarence, NY
Lines: 23

In article <MZb4w2600WB88M=4wv@andrew.cmu.edu>, kg19+@andrew.cmu.edu (Kurt A. Geisel) writes:
> I am trying to convert a TTL signal into an RS-232 signal.  I was
> under the impression that this can be done simply with the MC1488
> monolithic quad serial line driver.  Here is my set-up:
> ...
> When the TTL input is at 0 V, the RS-232 output is at 3.25 V.  When
> the TTL input is at +5 V, the RS-232 output is at 3.94 V.  Needless to
> say, this is useless.
> All the power supply lines have been check and re-checked.

	I bet you overlooked something...

> Do I have a bad chip or am I missing some glue?

	The 1488 is typically operated with a Vee of -12 to -15 volts and
Vcc of +12 to +15 volts.  According to your schematic (which I deleted for
brevity), you are using -5 volts for Vee and +5 volts for Vcc.  Use the
correct voltage range for Vee and Vcc and the chip should work just fine.

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