[E3-hacking] Another hello

Cliff Lawson clawson at amstrad.com
Thu Jan 19 16:49:23 GMT 2006

I'd have thought the protection was vital. It's not so much whether the PC
can detect the "weedy" 0V..5V swing coming out of an E2/E3 but whether the
UART input buffers on the OMAP/Sharp can stand getting -12V shoved up them
coming from the PC (I'm assuming that PCs still transmits true RS232 even if
they're a bit more lenient about what they can detect?)

(Or maybe my h/w designing colleague did splash for sufficient inbound
protection on the board - I can't remember off hand)


> -----Original Message-----
> From: Ian Stirling [mailto:ian.stirling at mauve.plus.com]
> Sent: 19 January 2006 16:44
> To: Discussion of the Amstrad E3 emailer hardware/software
> Subject: Re: [E3-hacking] Another hello
> Back in the dim and distant past, this may have been true.
> However, with the growth of low-power devices on the 232 bus, 
> more and 
> more stuff has quietly lowered the level at which 0 becomes 1 
> from 7(?) 
> of the MC1488/1489, down to 5V, or even lower.
> 5V signalling will work just fine with many of todays PCs, 
> even 3.3V on 
> quite a lot of them.

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