After receiving the grid-line draw control code, the data starting with
the first line and fourth column is assumed to be the grid line designation
data.
The designation data specifies on which character positions
(24 rows by 80 columns) the vertical and horizontal grid lines should be displayed.
The designation data defines the grid-line information for
each screen position from the first line, first column to the 24th line, 80th
column, respectively. It defines the grid lines for three columns using a
byte, so the length of this data is fixed-length 640 bytes as follows:
24 rows * 80 columns / 3 = 640
The following illustration shows the relation between the actual grid lines
on the display screen and the grid-line definition data.
Figure 1. Grid-Line Definition
Data and Displayed Grid Lines
The error process for the grid-line designation data is as follows:
If the first byte of the grid-line designation data is not X'27',
the grid-line definition data is ignored and the contents of the grid-line
information buffer are deleted.
Incorrect designation of the grid-line definition data:
If there is
a code other than X'40' to X'7F' in the grid-line definition
data with a length of 640 bytes, it is assumed to be an incorrect code and
the grid-line definition data after this code is ignored. The correct portion
of the grid-line definition data is displayed as the grid line on the screen
normally.
