[time-nuts] RS-232 Pin Outs for the Acron Zeit WWVB LCD Clock

Hal Murray hmurray at megapathdsl.net
Sun Jul 23 09:26:03 EDT 2017

TimeNuts at philipjackson.com said:
> I'm wondering if something like this $10 item
> http://www.nulsom.com/datasheet/NS-RS232_en.pdf 

That setup has a separate pin (hole?) for power.  It's setup to expect Gnd, 
Tx, Rx, and Pwr from the TTL side.

A previous message said the module designed for the job had a diode.  I'd 
expect that is using power from one of the modem control signals.

You could probably add a diode to make it work.

> I don't know if I've seen an inverting one and that would seem a more costly
> approach than handling the inversion on the clock board. 

Almost all TTL to RS-232 level shifter chips include an inverter.  It's just 
historical.  The first chips (MC1488, MC1489) did it that way and everybody 
who makes a new chip includes the inverter too so they can cleanly replace 
older chips.

These are my opinions.  I hate spam.

More information about the time-nuts mailing list