For those of you with an EPROM blower wanting to create your
own set of characters, the accompanying program will allow you
to easily create, change and amend each character cell. It is
written in machine code and will run under Nas-Sys.
As most of you are already aware, each character cell for
the N1 is made up of 16 rows of 8 dots whereas for the N2 it is
14 rows of 8 dots, the last two rows being unused by the N2. As
there are 128 characters in a character EPROM, the EPROM must be
16 x 128 bytes, ie. 2K. On executing the program you will be
asked whether you are programming an N1 or N2 EPROM followed by
the origin of the 2K of RAM where the characters will be stored.
Characters are produced by using the commands listed below and
storing them an tape ready for blowing into EPROM. (NB the
origin must be above 1700H)
will Fill the character RAM area with FFH. Thus,
unprogrammed locations will remain at FFH enabling you to
overprogram the characters at a later date.
will Increment the location number displayed in the
corner of the screen. This number corresponds to the
alphanumeric address given in your Nascom manual. For the
Graphics characters simply add 80H to the location
will Decrement the location number.
will Get a character from RAM specified by the location
number and place it into the character cell.
will Complement a character within the cell.
will Blank or clear the character cell.
will Reflect a character in the cell. This is very useful
when two characters are used to produce a symetrical
shape such as a pawn from a chess set.
will Save the character from the character cell into the
specified RAM location number.