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>Putting it All Together</TITLE
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>12. Putting it All Together</H1
><P
>The Xconfig file Table of Video Modes contains lines of numbers,
with each line being a complete specification for one mode of X-server
operation. The fields are grouped into four sections, the name
section, the clock frequency section, the horizontal section, and the
vertical section. </P
><P
>The name section contains one field, the name of the video mode
specified by the rest of the line. This name is referred to on the
"Modes" line of the Graphics Driver Setup section of the Xconfig file.
The name field may be omitted if the name of a previous line is the
same as the current line.</P
><P
>The dot clock section contains only the dot clock (what we've
called DCF) field of the video mode line. The number in this field
specifies what dot clock was used to generate the numbers in the
following sections.</P
><P
>The horizontal section consists of four fields which specify how each
horizontal line on the display is to be generated. The first field of
the section contains the number of dots per line which will be
illuminated to form the picture (what we've called HR). The second
field of the section (SH1) indicates at which dot the horizontal sync
pulse will begin. The third field (SH2) indicates at which dot the
horizontal sync pulse will end. The fourth field specifies the toal
horzontal frame length (HFL).</P
><P
>The vertical section also contains four fields. The first field
contains the number of visible lines which will appear on the display
(VR). The second field (SV1) indicates the line number at which the
vertical sync pulse will begin. The third field (SV2) specifies the
line number at which the vertical sync pulse will end. The fourth
field contains the total vertical frame length (VFL).</P
><P
>Example:</P
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>&#13; #Modename clock horizontal timing vertical timing
"752x564" 40 752 784 944 1088 564 567 569 611
44.5 752 792 976 1240 564 567 570 600
</PRE
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><P
>(Note: stock X11R5 doesn't support fractional dot clocks.)</P
><P
>For Xconfig, all of the numbers just mentioned - the number of
illuminated dots on the line, the number of dots separating the
illuminated dots from the beginning of the sync pulse, the number of
dots representing the duration of the pulse, and the number of dots
after the end of the sync pulse - are added to produce the number of
dots per line. The number of horizontal dots must be evenly divisible
by eight.</P
><P
>Example horizontal numbers: 800 864 1024 1088</P
><P
>This sample line has the number of illuminated dots (800) followed by the
number of the dot when the sync pulse starts (864), followed by the number of
the dot when the sync pulse ends (1024), followed by the number of the last dot
on the horizontal line (1088).</P
><P
>Note again that all of the horizontal numbers (800, 864, 1024,
and 1088) are divisible by eight! This is not required of the
vertical numbers.</P
><P
>The number of lines from the top of the display to the bottom form the frame.
The basic timing signal for a frame is the line. A number of lines will
contain the picture. After the last illuminated line has been displayed, a
delay of a number of lines will occur before the vertical sync pulse is
generated. Then the sync pulse will last for a few lines, and finally the last
lines in the frame, the delay required after the pulse, will be generated. The
numbers that specify this mode of operation are entered in a manner similar to
the following example.</P
><P
>Example vertical numbers: 600 603 609 630</P
><P
>This example indicates that there are 600 visible lines on the
display, that the vertical sync pulse starts with the 603rd line and
ends with the 609th, and that there are 630 total lines being
used.</P
><P
>Note that the vertical numbers don't have to be divisible by
eight!</P
><P
>Let's return to the example we've been working. According to
the above, all we need to do from now on is to write our result into
Xconfig as follows:</P
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>&#13;&#60;name&#62; DCF HR SH1 SH2 HFL VR SV1 SV2 VFL
</PRE
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></TD
></TR
></TABLE
><P
>where SH1 is the start tick of the horizontal sync pulse and SH2
is its end tick; similarly, SV1 is the start tick of the vertical sync
pulse and SV2 is its end tick. </P
><P
>To place these, recall the discussion of black magic and sync
pulses given above. SH1 is the dot that begins the leading edge of
the horiziontal sync pulse; thus, SH1 = HR + HGT1. SH2 is the
trailing edge; thus, SH2 = SH1 + HSP. Similarly, SV1 = VR + VGT (but
VGT is usually zero) and SV2 = SV1 + VSP.</P
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>&#13;#name clock horizontal timing vertical timing flag
936x702 65 936 968 1200 1232 702 702 710 737
</PRE
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><P
>No special flag necessary; this is a non-interlaced mode. Now
we are really done.</P
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