Re: MIL-STD-188-114A vs. RS-232
- From: "rickman" <spamgoeshere4@xxxxxxxxx>
- Date: 31 Mar 2006 04:14:02 -0800
Al Clark wrote:
I did a product many years ago that supported MIL-STD-188-114A (I think).
As I recall the main difference was polarity. They had a few other slew
rate issues I think as well. I'm fairly sure that we just used 189 and 188
type devices anyway and we never had an issue interfacing anything.
A typical 232 driver has something like a 300 ohm series R. This is to
protect it from shorts. You could probably add some Q's then then use a
series R
Thanks Al. The polarity is not important as it is programmable in the
FPGA. I had considered adding a separate TTL -> 114A interface using
discrete transistors, but your suggestion makes it simpler. I can just
use a complementary pair, each device in an emitter follower
configuration. With a Vcc of +-5 volt, this will pull to better than
the 4 volt minimum and a 50 Ohm resistor will provide the current
limit. We already have a SOT-23 dual transistor that should do the
job. I will have to add a voltage inverter to generate -5 volts. That
may be more difficult since I need a true -5 volts. A capacitor
inverter circuit using diodes will not get a full -5 volts. I guess I
could use FETs, or maybe I can find a very small IC to do the job.
Space on the board is very tight though.
.
- References:
- MIL-STD-188-114A vs. RS-232
- From: rickman
- Re: MIL-STD-188-114A vs. RS-232
- From: Al Clark
- MIL-STD-188-114A vs. RS-232
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