Zenith Data Systems Z-100 Series Installation Manual page 37

Page
3.7
General Theory of Operation
NOTE: The scan rate of the monitor cannot refresh the display faster
than 50 Hz.
Example for 50 Hz:
18,432/50
=
368.64 scan lines per frame
368.64/14
=
26.33
Note that the result of the above division is 26 with a remainder of 3.
Enter 25 (one less than the number desired) into register R4.
• Vertical Total Adjust Register (R5}- This 5-bit, write-only register
is used to lengthen the vertical total time to account for the scan lines
remaining when the value for R4 was determined. This value is ex-
pressed in scan lines. The correct value is 6 (06H).
• Vertical Displayed Register (R6}- This 7-bit, write-only register de-
termines the number of character rows which will be displayed. This
value cannot exceed, but may be equal to or less than, the value
in R4. The default value is 19H (25 decimal).
• Vertical Position Register (R7}- This 7-bit, write-only register con-
trols the position of the vertical sync expressed in character rows.
This value should be less than or equal to the value of R4. Entering
a lower number will move the display downward, higher values move
the display upward. The default value is 19H (25 decimal).