Vector 4 - Page 71

VECTOR GRAPHIC INC.
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As indicated in the previous chart the 6545A-1 has numerous registers. These
registers can be functionally divided into three groups: Status Register,
Address Register and Configuration Registers. The Status Register is used to
find the status of the Video Controller chip.
The contents of the Address Register are used to point (provide an address) to
one of 17 Configuration Registers. The Vector 4 uses 14 Configuration
Registers. These registers along with their values for each of the two major
modes are listed below.
Register Modes |
Number Eunction Alpha Graphies *
0 Horiz. Total 49 49
1 Horiz. Displayed ' 40 40
2 Horiz. Sync Position 43 43
3 VSYNC / HSYNC Widths 85H 85H
4 Vert. Total 25 295
S Vert. Total Adjust. 2 2
6 Vert. Displayed (#Char Rows) 24 24
7 Vert. Syne Position 24 24
8 Mode Control 10H 00H
9 No. of Scan Lines 12 | 12
10 Cursor Start 0 0
11 Cursor End 0 | 0
12 Display Start Addr. (HIGH) 38H **
13 Display Start Addr. (LOW) 00H **
Includes High Resolution, Gray and Color scale modes.
Represents address 0F000H.
These register values are inserted during system initialization by the system
software. Register 8 is adjusted for the graphics mode so that the left most
pixel positions can be aligned with the the left most margin. Values in
registers 12 and 13 represent the first or beginning address of the screen
display. This address can be changed to a new value (only on even boundaries)
if you want the first character (top left portion of screen) to have a different
memory location. The other register values are also under software control and
can therefore be modified to suit your particular video application. The
procedure used to accomplish these changes is described in the VECTOR 4
PROGRAMMERS GUIDE.
Display Modes
Before discussing how the Video Controllers' addresses are multiplexed it is
necessary to define the several types of video display modes. These modes can
be grouped into two general categories: Alpha and Graphies.
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