| 摘要 |
A video board in a personal computer supports a 2-gray level monitor as well as a 4-gray level monitor, by serving both the 1-bit plane video board operation and the 2-bit plane video board operation. A video output controller, having a shift register, a jumper and a divider, generates video output signals according to the selection made between the 1-bit and the 2-bit plane video boards. The shift register shifts the inputted data according to the order of the clock pulses. In the case of the 1-bit plane video board operation, eight clock pulses are supplied with a clock pulse input line connected to the clock generator output line by the jumper, while in the case of the 2-bit plane video board operation, four clock pulses are supplied with the clock pulse input line coupled to the divider by the jumper. The frequency of the clock pulses from the clock generator is divided by 2 through passing the divider. The decision of the operations of each bit plane video board is made by the jumper.
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