wampler@unmvax.UUCP (04/25/85)
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The Data General One is ALMOST compatible with the IBM. A MAJOR
difference is the serial ports. The DG/1 uses 8251 serail chips instead
of the 8250 (I guess no cmos 8250's?). At any rate, no standard PC
terminal program will work. I would like to get KERMIT up on the DG/1.
This requires knowing how the 8251's are connected to the interrupt
controller, etc. DG apparently hasn't released the tech manual yet.
Help! Does anyone know how to use the DG/1's serial ports
in interrupt mode? Has anyone seen the tech manual?
Bruce Wampler { ucbvax!unmvax!wampler }
Dept. of Computer Science
Univ. of New Mexico
Albuquerque, NM 87137 (505) 281-1307tsc2597@acf4.UUCP (Sam Chin) (04/26/85)
<>
I have used the DG One but know nothing about the internals. However, the
difference between the 8250 and the 8251 is that the 8251 gets its clock
from an external timer such as the 8253. The 8253 has normally 3 counters.
On the PC only one is available (the others are used for the speaker etc)
for a real time clock interrupt and is wired to the 8259 interrupt
controller which is then multiplexed into the 8088. Since the DG One is
fairly compatible with the PC, I would assume that the 8259 is at the same
port location and that it uses the same flag as on the PC. You can find out
what port your 8251 output is connected to by outputting a byte to each of
the 255 ports until you get something coming out (open your drive doors first
because you might mess with the disk i/o ports). Normally the status port is
the previous or next port address. To set the baud rate, you probably have
to figure out which counter the DG uses to put the divisor on the 8253. It
is possible that there are more than 1 8253's or a real time clock chip.
Hopefully the crystals are at the same speed. I have succesfully brought up
file transfer programs on antique Z-80 machines this way. Good Luck.
Sam Chin
allegra!cmcl2!acf4!tsc2597
tsc2597.acf4@nyu