Dynapro Technologies Dynapro ET TCS, Руководство разработчика приложений

Страница: 123 / 337

5-36
'RZQ/LQH/RDG&KDUDFWHU)RQW&RPPDQG^)'/&)`5HPRWH
The Down-Line Load Character Font Command allows the host to place custom characters into
Dynamic Character Fonts 1 and 2. Then, when the dynamic character font is mapped into the
Standard or Extended character set, the custom characters can be displayed.
For example, to create a dynamic character font that is only slightly different from the Static
ASCII Character Font, one method is to use the Down-Line Load Character Font command to
down-line load an entire new font of 128 characters into the Dynamic Character Font. This can
be somewhat tedious because all 128 characters, including characters which match those already
stored in the Static ASCII Character Font, first have to be developed by the host application. A
simpler method is as follows:
•
Using the Copy Character Font command, the host program copies the Static ASCII
Character Font into the dynamic character font of interest.
•
Using the Down-Line Load Character Font command, the host program replaces only those
characters in the dynamic character font that differ from the contents of the Static ASCII
Character Font.
•
Using the Map Character Font command, the host program maps the custom dynamic
character font into the appropriate character set (in this example, the Standard Character Set).
If the contents of either Dynamic Character Font is changed by the Down-Line Load Character
Font command while the Dynamic Character Font is mapped into either the Standard or
Extended character sets by the Displayed Screen, the changes immediately become visible on the
display.
Before down-line loading into a dynamic character font, the programmer should be aware of the
effects that the dynamic character font may have if its default contents are changed and then
mapped into one of the character sets.
Character positions within each character font are numbered from 1 through 128 (decimal);
communications codes that access the Standard Character Set range from 0 through 127
(decimal); and those which access the Extended Character Set range from 128 through 255
(decimal). Programmers should use care when determining the code value that must be sent to
access a given character. Table 5-4 shows the relationships needed between a character’s position
in the font and its corresponding communication code once the character font has been mapped
into a character set.
(1&2',1*&86720&+$5$&7(56)25'2:1/2$',1*
The character fonts store sixel data in cells 8 dots wide by 10 dots high. Each dot in the cell is
represented by a bit with a binary value of 1 or 0. A one (1) specifies that the dot becomes the
foreground color and a zero (0) specifies that the dot becomes the background color.
For example, to place the character A into a dynamic character font, the first step is to design the
character as shown in Figure 5-6.