24 Jul
2010
24 Jul
'10
11:47 a.m.
On Fri, 23 Jul 2010, Tony Duell wrote:
That is why I specified 'PC Async port'. I was refering to the standard
Async port found in an IBM compatible, nothing more. In other words I
would not expect the secondary (back) channel. Just pins 2-8, 20 and 22.
That's the subset on the DE9 connector too of course.
FWIW, I wouldn't expect the current loop interface that was on the
origianl IBM Async card. And I was using the accepted common meaning of
'PC', while I consider the HP9830 to be one of the first personal
computers, I wouldn't expect a USB-RS232 interface to do all that the
11284 interface for the HP could do...
Actually, do the USB-RS232 adapters (I refuse ot
say USB-serial, since
there are many, many serial interfaces, including USB itself) allow you
to do all you can do with aa PC Async port? Like setting odd baud rates?
Or 5 bit mode (yes, I do sometimes want to talk to ta Creed 7)
How could it?
Do they implement the full 25 lines? Or, just the DB9 subset (1 through 8
and 20) They might not even implement the complete DE9 subset.
That's really what I was asking, along with can it do all that hte
8250/16450/16500/etc can do.
Although MOST devices can be connected using a subset, EVERY one of the 25
lines has a purpose, even having separate signal and chassis grounds.
The RS232 spec I work from has a few pins labelled 'reserved', so perhaps
not all 25 are used. But a lot more are defined than are commonly used on
micros/. There's a complete second serial channel, for example (very few
micros implemented that -- the HP Integral is one of the few that
does...). And clock I/O for synchronous modes
-tony