on the programmer’s ZIF socket. In practice,
however, we found that the lever had to be
lifted ever so slightly to enable the circuit to
be inserted into the socket. The above tip,
may, therefore, not be applicable in all cases.
Finally…
With the board fully stuffed and the battery
connected, the emulator is, in principle, ready
for use. First, however, we recommend run-
ning a few function tests.
The operation of the GAL may be checked
by pressing S1. LED D5 should light and go
out again when S2 is pressed once more.
Now insert the EPOM emulator into the IF
socket of your programmer and then press S1.
Run a Blank Check on the programmer. If
everything works as it should, the program-
mer should report an empty (blank) EPROM.
Now press S2 to force the emulator into Nor-
mal mode. Next, run another Blank Check on
your programmer. This test should also be
completed without problems, proving that
each and every mem-
ory location in the
emulator RAM (IC3)
contains the value FF.
As a final test, we
can check the pro-
gramming. Choose an
arbitrary programming
file on the programmer
and ‘burn’ it into (emu-
lated) EPROM. LED D4
should light. Next, run
a Verify operation to
see if the program-
ming operation was
successful.
If a problem is
encountered, carefully
inspect the construc-
tion of your emulator.
Check the orientation
of the ICs, diodes, etc.,
as well as the value of
all components. Also
inspect the solder
joints for short-circuits
and/or dry joints.
One more tip: temporarily install a ZIF
socket in the EPROM socket of the target cir-
cuit. This allows the emulator unit to be
inserted and removed as many times as nec-
essary without the risk of bad contacts
between target circuit and emulator. The
cheaper brands of IC sockets which prolifer-
ate in the hobby circuit these days are prone
to developing contact problems when used
more than two or three times.
(024066-1)
Power supply
The complete circuit is powered by
a 9-volt battery. Purposely no provi-
sion is made for the circuit to be
powered from the +5-V supply pin of
the EPROM. After all, the voltage at
this pin may 6 V during
programming, which is not a healthy
level for the ICs in the emulator. If
you do want to employ this voltage,
measures should be taken for it to be
stabilised at +5 V. A DC-DC con-
verter could be used for this pur-
pose, but the disadvantages will
always outweigh the benefits,
mainly because the circuit becomes
bulky and difficult to work with in
practice. The battery can be elimi-
nated anyway because the circuit is
not permanently connected to an
external power supply which would
guarantee that the RAM contents
are not lost or corrupted the instant
the emulator is removed from the
programmer and taken to the
EPROM socket of the target system.
Construction
The artwork of the printed circuit
board designed for the EPROM emu-
lator is shown in
Figure 6
. The
board allows the unit to be compact
and easy to handle. Construction is
easy by almost any standard. As
customary, it is best to start with the
lower profile components (in this
case, the horizontally mounted resis-
tors). Then follow the other discrete
parts, the integrated circuits and the
pushbuttons. Two points are worth
noting. The first concerns the emu-
lator connections marked ‘IC2’.
These consist of two rows of 14-way
pinheaders whose pins have to pro-
trude downwards, requiring the
headers themselves to be soldered
at the
underside
of the PCB, too.
This is best done with the ICs
already mounted. A further pint to
note is that IC3 is mounted
above
IC4 and IC5. The latter two have to
be soldered on to the board first,
while IC3 is fitted with a raised
socket. This is conveniently made
from two 14-way pinheaders. As a
matter of course, IC4 and IC5 are
mounted without sockets, else IC3
would require a second socket! By
the way, note the position of IC3:
viewed from above, it should be at
the right-hand side of connectors for
‘IC2’.
Here are some more practical
details. The holder for the 9-V bat-
tery may be secured to IC3 using
two-sided sticky tape to make the
unit sturdy and compact. It may also
be a good idea to file a away a small
piece of PCB material to the left of
diode D1 to make room for the lever
MICRO
PROCESSOR
17
11/2002
Elektor Electronics
Содержание EPROM
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