5 Mar
2004
5 Mar
'04
3:11 p.m.
Hi Joe
The 7109 was made by many manufactures and is a common
A/D. It is a dual slope type. Quite accurate when comparing
to a reference. It has one funny feature that isn't usually
mentioned in the data sheets. If you get an over range,
it will transfer some additional energy to the Auto-Zero
capacitor. This can take many convertion cycles to recover from.
When used with an input mux, make sure that you either have
a wait after overrange or some way to clamp it below full
scale. Even a single lsb of overscale has significant effect
because of the amplification used to do the auto-zero. A single
lsb of overscale can be over 100 lsb's on the next read,
depending on the A-Z capacitor size. Not good when you are
looking to get the most out of the 12 bits.
As for the board, maybe just some tracing out will determine
the addressing so that you can play with it. I have a
80C188 processor board for the STD with a Forth in Flash
on it. I find Forth to be real handy for poking ( and peeking )
at unknown boards such as these.
Dwight
From: "Joe R." <rigdonj(a)cfl.rr.com>
Yesterday I picked up two shoebox sized units that were marked as
"enviromental units". However they had lights marked Tx, Rx, etc and a Comm
port. Inside it had a STD bus chassis with three cards installed. On has a
80C31 CPU, one has a Zilog Z0853004 comm chip and the other has a MAXIM
ICL7109CPL A/D convertor. The first two cards appear to be custom made and
are probably useless for anything except the system they were designed for.
However the third card (with A/D) is a standard commercail product and was
made by WinSystems and is their model LPM/MCM-7109. Does anyone have any
data on this card? It's not on WinSystems website and I tried to contact
them and ask about it but they were less than cooperative.
Joe