Yup, I have to say I was surprised when folks were saying they could connect an E3 to a PC without a MAX232?! Both E2 and E3 signals are at TTL levels so, by rights, you shouldn't be able to just connect direct and have it work as the 16550 in the PC is supposed to be expecting RS232 -/+12 but maybe some of them are a bit more "lenient" ? Also, as Andy says, the E3 signals are inverted (saved the cost of an inverter on the board!) so we use MAX232 boxes with a switched 74 series inverter in there too and use it non inverted for E2 and inverted for E3. Your mileage may vary.
Cliff
-----Original Message----- From: Andy [mailto:andy@entropy.demon.co.uk] Sent: 18 January 2006 20:21 To: Discussion of the Amstrad E3 emailer hardware/software Subject: Re: [E3-hacking] Another hello
The short answer is what comes out is inverted, like RS232, but is not at valid RS232 voltage levels as it never swings negative. Some PCs might let you get away with this, many wont. Being already inverted connecting this to typical RS232 line driver chip then re-inverts the signal and that wont work either.
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