HP50g - RS-232 cable

[cyrille de brébisson]

Hello,

(10-11-2016 08:38 PM)mfleming Wrote:  As Cyrille mentioned the HP50 has a pretty wonky RS232 implementation
~Mark

Actually, the 50G does NOT have a RS-232 port. It has a serial port which is standard on pretty much all CPU these days.
As it turns out, the signal used by these serial port has exactly the same 'shape' as an old RS-232 (how strange :-) but uses positive logic and CPU voltages (0 to whatever GPIO voltage the chip is using)...

These types of serial ports were/are designed to let CPU communicate with each others easely, cheaply and with minimum silicone. I assume that they were designed using the same signal as RS232 because that was a singal shape that was working (and proven to do it)...

They just did not include voltage boosts (and negative logic) because it would have been expansive to place on chip.

Cyrille