Fluke PM6681 - Page 40

Figure
4-21
Block diagram, PM
6681 logical
circuits.
Logical
Circuits
•
Microcomputer
Circuits
including.
I/O
The
microcomputer
in
PM 6681
is
an Intel
16-bit
CHMOS
lacontroller
80C196KC16, U6. It is
a fast micro
controller, in-
tended
for
controller applications, i.e., it has
many I/O
ports
and other
facilities
to control and
react
on
the
external
world. It contains
232
RAM-bytes,
(see Figure
4-21).
The
micro
controller
can operate
in
both 8 and
16-bits
mode
externally.
Internally
the
micro controller
uses
16-
bits. The address
and data-bus ADO to
ADI
5
is
shared
(time
multiplexed) between
addresses and data.
Therefore
the
address
must be stored in an
address-latch (U14 and
U15) by using
the signal ALE (pin
62).
If
the surrounding
circuits
are slow compared to
the micro
controller,
wait states must
be
issued. The ready-pin
(pin
43)
goes
low to get wait states.
When
the micro
controller
communicates
with the battery RAM,
the GPIB-chip, the
ASIC;s,
and the trigger
level
circuits, wait states
are auto-
matically Inserted.
The
PROM;s (U16 and
U17) used is a 27H010,
i.e.,
two
128K byte memories.
The address mapping is
done so we
can only
address
32K bytes directly.
Bank
switching is
4-16
Hardware
Functional
Description