It would not be out of place to list here the various control codes and their
Code 02 (CTRL B) sets bidirectional print. This mode gives maximum throughput
– say 65 chars per second!
Code 03 (CTRL C) sets unidirectional print. This gives best alignment for
columns of figures. The command is obeyed immediately on receipt.
Code 04 (CTRL D) sets double width printing. This character is queued in the
buffer, and only takes effect in its appropriate place. It is automatically reset at
the end of a line.
Code 05 (CTRL E) sets single width characters. All lines start out in this
condition, so you must reindicate by a CTRL D if you want double width after each line
Code 08 (CTRL H) Backspace. This will only backspace within a line. It will
not pass a Line Feed (0A), a Carriage Return (0D) or a Form Feed (0C).
Code 09 (CTRL I) Horizontal Tab. This will cause the print head to print
spaces until it is at the next column which is a multiple of 8.
Code 0A (CTRL J) Line feed. This prints any preceeding characters in the
buffer, and advances the paper by one line.
Code 0C (CTRL L) Form Feed. This causes 6 line feeds in succession.
Code 0D (CTRL M) Carriage return. This causes any preceeding characters in the
buffer to be printed, and if the strap option is set in the IMP, causes a line feed.
Code 1F (CTRL _) Graphics Mode. Prints out the Buffer, and puts head at
lefthand side on a fresh line. Then it interprets the next 760 Bytes as a dot pattern,
and prints them across the page. At the end of the line, it feeds enough for another
graphics line to join below the last one, and the IMP returns to the normal type mode.
It is necessary to reinvoke the graphics option at the start of each line of graphics.
These are the options, with the addition of the self test on reset. Without
any doubt, the IMPRINT is a very worth while addition to any IMP. The alteration to
the rub out character to allow continuous bi-directional printing alone allows the
throughput of the IMP to be nearly doubled (38 chars per sec to 65 chars per sec from
my measurements!) and may put off the evil hour when a faster printer becomes
essential. Those who have had to wait two hours for the latest edition of a printout
will know what I mean (and sympathise?).
The IMPRINT comes with a well commented and well printed set of documentation.
There is one error in it that I found. The reference on page 3 to code 04 should be to
code 02. With my copy, there was no mention of how to put the EPROM in position. I
hope that this will be rectified shortly. To open the IMP, you will need a 3/32" Allen
hex key. Unplug the IMP from the mains (dying is something you usually only get one
chance at!) and open the two little black studs on each side with the Allen Key, which
can be got in any good toolshop or engineers providers. Very carefully, slip the case
off, and lay it on its back beside the machine. It is still connected to the IMP by a
loom of wire, so try not to put too much tension on these wires. Then, with a long
handled fine screwdriver, working from the front of the machine, insert the screw
driver under the EPROM, which is about 1/3 of the way across the machine, pointing
front to back. Very gently, you can twist the blade to free this EPROM, until it can
be lifted out. It should be held only by the ends, not by the pins. The new EPROM can
be placed in position, holding in the same manner, with the orientation dot or dimple
on the end facing the print mechanism, and pushed down gently into position. The old
EPROM should be placed into a piece of antistatic foam, or foil wrapped airfoam, and
kept until a use arises for it. It could be reprogrammed with a new character set for
an N2, or an N1 with Econographics. Having inserted the EPROM, now is the time to
lubricate the innards of the IMP. A drop of oil on the polished guide rail, the frame
edge, the helical cam, and the ribbon driver are all that is required. Now put the top
back, screw in the screws, thread the paper, and plug in. Turn on, hit reset, while
holding down the Line feed button. The machine will enter self test mode, and print
away busily for about 25 seconds. The rest is up to you!
The IMPRINT is available from Interface Components (and possibly other Nascom
distributors ?), costing #30 plus VAT. The author, David Parkinson, is to be
congratulated on having got so much into so little.