JPH1034896A - Laser beam printer video signal output circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a serial video signal by a video clock having a relatively low frequency by generating a clock synchronizing pulse tuned with the video clock and having a narrower width than the clock, and using a delay pulse sequentially delayed from the synchronizing pulse. SOLUTION: An input video signal is stored in a video memory 1. A parallel video signal (a) from the memory 1 is temporarily latched to a latched circuit 3 as parallel data according to a video clock (d) generated from an oscillator 2. A monostable multivibrator 4 sequentially generates a clock synchronizing pulse (e) having a pulse width of one divided by several of latched parallel data of the block (d) in synchronization with the clock (d). Delay circuits 5-1 to 5-7 output delay pulses sequentially delayed from the pulse (e). A composite circuit 6 combines parallel data signal from the circuit 3, the pulse (e) and the delayed pulse, and outputs a serial video signal (m).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam printer video signal output circuit, and more particularly to a laser beam printer video signal output circuit for converting a video signal which is parallel data into serial data and outputting the serial data.

[0002]

2. Description of the Related Art A conventional laser beam printer video signal output circuit will be described in detail with reference to the drawings.

FIG. 4 is a block diagram showing an example of the related art. The laser beam printer video signal output circuit shown in FIG. 4 includes a video memory 11, an oscillation circuit 12,
And a serial conversion circuit 13. FIG. 5 is a time chart showing the operation of the laser beam printer video signal output circuit shown in FIG. The parallel video signal a from the video memory 11 is
The video signal c is converted into a serial video signal b by the parallel / serial conversion circuit 13 at the timing of the video clock c, and transferred to a display (not shown).

[0004]

The above-mentioned conventional laser beam printer video signal output circuit requires the video clock frequency to increase as the recording speed increases.
There is a problem that the operation limit of the parallel / serial conversion circuit is exceeded.

[0005]

According to a first aspect of the present invention, there is provided a laser beam printer video signal output circuit comprising a video memory for storing an input video signal, an oscillation circuit for generating a video clock, and a parallel video signal from the video memory. A latch circuit that temporarily latches the data as parallel data according to the video clock, a monostable multivibrator that generates a clock synchronization pulse synchronized with the video clock, and a plurality of circuits that sequentially delays the clock synchronization pulse and outputs a delayed pulse. A delay circuit; and a combining circuit that combines the parallel data signal from the latch circuit, the clock synchronization pulse, and the delay pulse to output a serial video signal.

According to a second aspect of the present invention, in the laser beam printer video signal output circuit according to the first aspect, the pulse width of the clock synchronizing pulse is a time which is 1 / the number of latch parallel data in the cycle of the video clock.

According to a third aspect of the present invention, in the laser beam printer video signal output circuit according to the first aspect, the delay times of the plurality of delay circuits are the same as the pulse width of the clock synchronization pulse.

[0008]

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. A laser beam printer video signal output circuit shown in FIG. 1 includes a video memory 1 for storing an input video signal, an oscillation circuit 2 for generating a video clock d, and a parallel video signal a from the video memory 1 which is parallelized in accordance with the video clock d. A latch circuit 3 for temporarily latching as data, a monostable multivibrator 4 for generating a clock synchronization pulse e synchronized with a video clock d,
The clock synchronization pulse e is sequentially delayed and the delay pulses f and g
..... delay circuits 5-1 and 5-2 for outputting l
.. 5-7, a parallel data signal from the latch circuit 3, a clock synchronization pulse e, and delay pulses f, g,.
and a synthesizing circuit 6 for synthesizing 1 and outputting a serial video signal m.

FIG. 2 is a time chart showing the operation of the laser beam printer video signal output circuit shown in FIG. The pulse width of the clock synchronizing pulse e is a time equal to the number of latch parallel data in the cycle of the video clock d. The delay times of the delay circuits 5-1, 5-2,..., 5-7 are the same as the pulse width of the clock synchronization pulse e.

FIG. 3 is a time chart showing the relationship between the output serial video signal m of the synthesizing circuit 6 shown in FIG. 1 and the video clock d.

[0012]

The video signal output circuit of the laser beam printer of the present invention generates a clock synchronization pulse having a width narrower than the video clock in synchronization with the video clock, and uses a delayed pulse obtained by sequentially delaying the clock synchronization pulse. This has the effect that a serial video signal can be obtained with a video clock having a relatively low frequency.

[0013]

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a time chart illustrating the operation of the present invention.

FIG. 3 is a time chart for explaining the operation of the present invention.

FIG. 4 is a block diagram showing an example of the related art.

FIG. 5 is a time chart showing the operation of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Video memory 2 Oscillation circuit 3 Latch circuit 4 Monostable multivibrator 5 Delay circuit 6 Synthesis circuit

Claims (3)

[Claims] A video memory for storing an input video signal; an oscillation circuit for generating a video clock; a latch circuit for temporarily latching a parallel video signal from the video memory as parallel data according to the video clock; A monostable multivibrator for generating a clock synchronization pulse synchronized with a video clock, a plurality of delay circuits for sequentially delaying the clock synchronization pulse and outputting a delay pulse, a parallel data signal from the latch circuit and the clock synchronization pulse, A synthesizing circuit for synthesizing the delay pulse and outputting a serial video signal. 2. The pulse width of the clock synchronization pulse is:
2. The laser beam printer video signal output circuit according to claim 1, wherein the period of the video clock is 1 / the number of latch parallel data. 3. The laser beam printer video signal output circuit according to claim 1, wherein a delay time of said plurality of delay circuits is equal to a pulse width of said clock synchronization pulse.