Thank you, Jim.

I'll keep them in my mind. But from the first glance:
 I need:
 1. Wider input gap.
 2. Higher bottom threshold.
 3. Lower input impedance.
 4. Ability to work from open collector source.
 5. Some flexibility to cope with other requirements.

 Mike.

Jim wrote:
> Mike, have you considered simply using something
> from the MC1489, MC14C89, SN75189, SN75C189,
> DS1489, and DS14C89 family RS232 line receiver
> family?
>
> This chip series is basically billed as a:
>
>   "ESD-Protected, Quad, Low-Power RS-232
>    Line Receiver"
>
> but will work to 'detect' TTL  and CMOS logic
> levels *and* is protected for electro-static
> discharge ...
>
> Brief specs:
>
>  Input low:     approx. 1 V
>  Input high:    approx. 2 V
>  Working range: +- 25V
>  Approx Rin:    5 KOhms

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads