27 Aug
2007
27 Aug
'07
12:33 p.m.
Sellam Ismail wrote:
As you can see from the manual there are two RS-232 serial interface options
but they require the appropriate firmware EPROM being present and a small
adapter which plugs into the parallel(!) plug. My unit had the firmware but I
didn't get the hardware adapter, but it turned out to be quite simple to build
an adapter with a MAX-232 chip.
This may all be more than you want to deal with right now if you are just
trying to program some 2716s but if you really want to know what your units are
capable of you need to look at the labels on the installed firmware EPROMS and
correlate them with the options codes/list in the manual.
Brent Hilpert sayeth:
(It's worse than that, in addition to all the 4004 family chips there are
other 'standard function' chips in odd format: some Signetics TTL that don't
match directly to 7400 series and which have a habit of failing; the data
buffer is composed of type 6508 CMOS RAM chips. Even the LEDs on the 2716
module, which look like ordinary individual LEDs, turn out to have internal
current-limiters so you have to add a resistor if replacing them.)
Speaking of the Signetics chips, if you wish to take the time on a crap shoot,
here's one thing you might wish to try to repair the 2716 module:
The problematic Signetics ICs are type 7234(mil-spec)/8234(commercial) (they
are just TTL quad 1-of-2 tri-state muxes but different pinout/control from
7400 types). I have had 2 or 3 of these ICs fail in my unit. There are 2 of
them in the 2716 module. You might try scavenging two from the non-working
base unit and replacing them in the 2716 module to see if it then functions in
the good base unit.
Note: in idle-state with no 2716s in the MASTER/COPY ZIF sockets the 8 data
LEDs on the 2716 module should be ON (open-circuit default to high).
I've had a few problems with mine, mostly
failing semiconductors, all of
which have been unusual and difficult to replace/substitute, although I
was quite pleased when I found the 4004 inside.
I'll say. It's basically a 4004 microcomputer system in there, so it's no
surprise the support chips have been hard to track down.
IIRC, some of
the communication adapters if plugged in (serial¶llel
D plugs) may cause the unit to appear hung.
Interesting. But nothing is plugged into those. Interestingly, the
serial interface is current loop, for interfacing to a TTY. That feature
really dates these things :)