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)
Cliff
-----Original Message----- From: Ian Stirling [mailto:ian.stirling@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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