FPD85308 datasheet(29/31 Pages) NSC

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APPENDIX A: GPO Programming

Examples (Continued)

GPO Programming Example #3:

Generate a control signal which toggles during horizontal

blanking and alternates polarity each frame. This control

signal is used as the reversal signal.

Horizontal time (clocks/line) = 1300 dot clocks

Vertical period (lines/frame) = 850 lines

Control is active beginning at line 1 and remains active for

769 lines.

(Odd number programmed in Duration Register causes con-

trol signal to alternate polarity each frame)

GPO Vertical Start Register = 1

GPO Vertical Duration Register = 769d (301h)

Positive going pulse causes output to toggle. Edge occurs

20 output clocks after end of each line (1024/2 + 20 = 532).

Pulse duration is not critical since the output will be in toggle

mode. (Dual Bus output clock = 32.5 MHz for 65 MHz XGA

video, 1024 pixels/line, 768 lines/frame).

Note: 6 counts are added to the output start # because the GPO pixel count

begins 6 clocks prior to the output data.

GPO Horizontal Start Register = 538 (238h)

GPO Horizontal Duration Register = 10d (0Ah)

The control pulses are positive (bit [0] = 0) and the toggle

circuitry is enabled (bit1 [1] = 1).

GPO Control Register = 2

(For a second control signal of opposite polarity, program

another GPO Control Register with same count values with

GPO Control Register = 3.)

DS101356-25

FPD85308 датащи(PDF) 29 Page - National Semiconductor (TI)