28 Apr
2005
28 Apr
'05
11:40 a.m.
I'm trying to use the DECmate/VT278 in terminal emulation mode (VT100)
via the serial board/DP278, but at this mode all the docs says that
it's only restricted 4800.
Has anybody done it or is it possible to up the speed to at least 9600?
Is this a hardware or firmware limitation?
/wai-sun
28 Apr
28 Apr
12:03 p.m.
On 4/28/05, Wai-Sun Chia <waisun.chia at gmail.com> wrote:
I'm trying to use the DECmate/VT278 in terminal
emulation mode (VT100)
via the serial board/DP278, but at this mode all the docs says that
it's only restricted 4800.
Has anybody done it or is it possible to up the speed to at least 9600?
Is this a hardware or firmware limitation?
Since the 6402 will easily handle speeds over 4800, I _think_ the
limitation is how fast the CPU can emulate a VT100, not how fast can
the UART accept characters, so given your choices, I'd say it's a
firmware limitation.
-ethan
6:35 p.m.
Has anybody
done it or is it possible to up the speed to at least 9600?
Is this a hardware or firmware limitation?
Since the 6402 will easily handle speeds over 4800, I _think_ the
limitation is how fast the CPU can emulate a VT100, not how fast can
the UART accept characters, so given your choices, I'd say it's a
firmware limitation.
11:38 p.m.
On 4/29/05, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Not necesarily. The 6402 takes external transmit and
receive clocks, at
16 times the desirted baud rate. If the clock generator hardware can't go
faster than 16*4800 for some reason, then you won't get more than 4800
baud. This is probalby very easy to modify, though.
Sorry to sound simplistic, but does that mean if I just whack in an
appropriate crystal, then I'd magically get 9600? (haven't downloaded
the prints yet)
Recommendations for an appropriate crystal would be very much appreciated! :-)
How much do you think I could up it to? 19k2?
/ws
29 Apr
29 Apr
4:50 a.m.
Datasheets for the Harris version of the UART (HD6402) specify a maximum clock rate of 2
MHz and hence a maximum baud rate of 125 KHz (2000/16).
If the current baud rate generator crystal is greater than 16*4800=76.8KHz then it (may)
be possible to simply bypass some dividers on the board rather than finding/installing a
new crystal.
Wai-Sun Chia wrote:
On 4/29/05, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Not necesarily. The 6402 takes external transmit
and receive clocks, at
16 times the desirted baud rate. If the clock generator hardware can't go
faster than 16*4800 for some reason, then you won't get more than 4800
baud. This is probalby very easy to modify, though.
Sorry to sound simplistic, but does that mean if I just whack in an
appropriate crystal, then I'd magically get 9600? (haven't downloaded
the prints yet)
Recommendations for an appropriate crystal would be very much appreciated! :-)
How much do you think I could up it to? 19k2?
/ws
6:19 p.m.
On 4/29/05, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I've not looekd at the prints, but I'd be wary of changing a crystal. It
may well be used for the CPU clock, or video timing, or something like
that.
I'd try to figure out the divider chain, and see if you can connect the
UART clock pins to something twice as fast (i.e. one binary division
stage less).
-tony
Not necesarily. The 6402 takes external transmit
and receive clocks, at
16 times the desirted baud rate. If the clock generator hardware can't go
faster than 16*4800 for some reason, then you won't get more than 4800
baud. This is probalby very easy to modify, though.
Sorry to sound simplistic, but does that mean if I just whack in an
appropriate crystal, then I'd magically get 9600? (haven't downloaded
the prints yet)
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days inactive
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ard＠p850ug1.demon.co.uk -
ethan.dicks＠gmail.com -
hilpert＠cs.ubc.ca -
waisun.chia＠gmail.com