INMC 80 News


May–September 1981 · Issue 4

Page 58 of 71


The IMPRINT: a review.

Rory O’Farrell

The IMPRINT is a new operating system for the IMP printer. It comes in the form of a new EPROM, which is substituted for that provided as standard in the IMP. With the addition of this EPROM, your IMP has a number of important new facilities.

Firstly it has the facility, under software control, to print either normal sized characters, or double sized characters, which it prints 40 to the line. All characters can now be printed unidirectionally or bidirectionally, by sending the correct control code to the IMP. The IMP can also interpret Control I as a tab character, and steps across the page to the next multiple of 8 columns, thus becoming compatible with the Tab function under the CP/M disk operating system. Control L (code 0C) is recognised as a form feed command, and causes the IMP to advance the paper by six lines.

Connection of the IMP to your system remains unchanged, the Busy line behaving as previously. The new system immediately makes the IMP sound different. The reason is not hard to find. Examination of the manual discloses that the IMP is effectively printing at twice the speed (unless you have been changing the preset power up options). Gone is the change to unidirectional printing when there are more than forty characters on a line- Why doesn’t the head overheat? The manual explains that the head is rated for continuous printing, and the only character which caused occasional difficulty was the rubout character – the white block. This character has now been changed to an inverted ? , and in consequence 80 characters per line can now be printed in bidirectional mode. This option can be disabled under software control, so that when best alignment is required in the type it can be obtained by selecting the unidirectional mode.

If the Line Feed button is held down as Reset is pressed on the IMP, it will immediately set to, and print its character set four times, both in standard and double width. When you have installed the EPROM, this is the easiest way to check that all is as it should be.

What happens if you have an application which demands heavy lines across the page, as it might be, lines of the old 7F white Block? All is not lost! The IMP has one surprising addition:

A Hi Res Graphics Facility!!!

This facility, in addition to the previously mentioned facilities, make the IMP unsurpassed value for money! It now acquires the facility to plot hi res graphics all across the page, on receipt of a 1F code (control _). When it receives this character, it prints out what is left of the buffer, goes to the lefthand side of the print area, and feeds to a new line. It then proceeds to gather the next 760 Bytes, and interpret the 7 least significant bits of each byte as instructions for each print needle (bit 6=top dot, bit 0=bottom dot). When it has these 760 bytes (they take a fair while to send – over 6 secs at 1200 baud) it prints the line. In printing the line, it takes account of the head specification, which says that a dot can not be printed in two columns in succession, and if it finds such an illegal condition, it resets a dot or dots. To indicate that it has interfered with your data, it turns on the Red Error LED, and turns it off at the end of the line. This allows you to plot 380 dots across the width of the page at any one time, and you have 760 columns at your disposal. When the graphics line is finished, the IMP feeds by the amount of the line only, so that another graphics line can be printed below and immediately contiguous. In this way it will be possible to plot quite fine resolution graphs, displays and pictures. I have in mind using the IMP to plot soil resistivity data from Archaeological surveys, which I had been asked to process. The plot from the IMP will very quickly give an indication of the result, without having to go to the trouble of doing a detailed manual plot.

Page 58 of 71