27 Apr
2010
27 Apr
'10
12:43 p.m.
The tty interface on this SDK-85 was built for 20mA
current loop so I'll
have to either rework that to RS232 or invent a new method to offload.
But not a big deal really.
I would be _very_ supprised if that serial interface doesn't sue some
TTL-level serial chip (or bit-banged through a TTL level port) followed
by a current loop interface.
In which case, since you need output only, grab
the TTL leve signal at
the input to the coverter and feed it into something like a MAX232 (or a
1488 if you have +/-12V suppleis around).
No need. The SDK can be via jumpers wired with run RS232 levels
for terminal. A minus 5 to 12 Volt supply is required but we are
talking a few milliamps.
The intel i8085 manuals had the schematic for the SDK85.
So does the book I've just pulled off my bookshelf ('Microcomputer
Theory and Applications wit hteh Intel SDK-85'). I can't find any links
to set RS232 levels on the serial port. The current loop converter is a
simple trasistor stage (PNP transsitor), emiter to +5V, collector to the
current loop through a resistor. Now, IIRC, the current loop passes
current in the idle state (whcih implies that transistor is turned on in
the idle state), but the RS232 signal is -ve in the idel state. So you
need an inverter.
I wonder (and I've not got an SDK85 to try it with). If you connected a
suitalbe pull-down resistor (say 1k) between the current loop +ve output
(pin 13 of J7 on my schematic) and ground, and then also connected pin 13
of J7 to the input of an RS232 driver, would that work? I think so.
Incidnetlaly, the book also has the monitor source lisitng in it. I don't
feel like typing it in, though :-)
-tony