HaraldS
Well-Known Member
Re: Can I see some light ahead?
Hi Jeff,
Looks like you found the spec. Great. I have been using this chip as NMEA driver for my own little microprocessor controlled gadgets, so I have driven it at TTL level. The enable pin is positive true, and as you said turns on the output, if tied to ground the outputs will float at high impedance. You can leave it on high all the time for RS422, and as you guessed it is good practice to put a resistor between Vcc and that pin. Between 1k to 10k will always be fine.
You probably found the drawing of the RS232 to RS422 level converter on that sheet, that’s what I described. Looking at it again I think there might be a slight mistake in the drawing, in that the 10k resistor at the chip input should actually go in series with the RS232 input.
If you need to go the other way round, from RS422 to RS232, best would be to take the matching RS422 receiver, type LTC 488/489 and drive it with an RS232 receiver.
I have been using the MAX232 as RS232 transceiver, it works both ways and has an easy way to generate the +/- 9V needed for RS232 from 5V, with just a few capacitors in addition to the IC.
Good luck,
Harald
<A target="_blank" HREF=http://www.taniwani.de>http://www.taniwani.de</A>
Hi Jeff,
Looks like you found the spec. Great. I have been using this chip as NMEA driver for my own little microprocessor controlled gadgets, so I have driven it at TTL level. The enable pin is positive true, and as you said turns on the output, if tied to ground the outputs will float at high impedance. You can leave it on high all the time for RS422, and as you guessed it is good practice to put a resistor between Vcc and that pin. Between 1k to 10k will always be fine.
You probably found the drawing of the RS232 to RS422 level converter on that sheet, that’s what I described. Looking at it again I think there might be a slight mistake in the drawing, in that the 10k resistor at the chip input should actually go in series with the RS232 input.
If you need to go the other way round, from RS422 to RS232, best would be to take the matching RS422 receiver, type LTC 488/489 and drive it with an RS232 receiver.
I have been using the MAX232 as RS232 transceiver, it works both ways and has an easy way to generate the +/- 9V needed for RS232 from 5V, with just a few capacitors in addition to the IC.
Good luck,
Harald
<A target="_blank" HREF=http://www.taniwani.de>http://www.taniwani.de</A>
