Pulse width modulation signal generating circuit
AssigneeNEC Corporation
InventorKazunari Shimohara
Life of this patent
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Abstract
A microcomputer having a signal generating circuit which generates pulse width modulation signals defined by a carrier wave, and which controls controlled portions according to pulse width modulating signals. The signal generating circuit comprises a carrier wave defining timer which outputs a value varying the same as a waveform providing a carrier wave, a control register which controls the time period of the timer, a reload register which holds a count value, control blocks which generate pulse width modulation signals according to the value of the timer and the count value of the reload register.
Claims3
A microcomputer having a signal generating circuit provided on a semiconductor substrate for generating pulse width modulation signals defined by a carrier wave, for the purpose of controlling a unit to be controlled in accordance with the pulse width modulation signals, said signal generating circuit comprising:
- a carrier wave defining timer for outputting a value that varies the same as a waveform providing said carrier wave;
- a control register for controlling a period of said carrier wave defining timer;
- a reload register for holding a counting value;
- control blocks each for generating said pulse width modulation signals on the basis of a value of said carrier wave defining timer and said count value held in said reload register;
- each of said control blocks comprising;
- a compare register for ceaselessly comparing the value of said carrier wave defining timer with a comparison value, and outputting a coincidence detecting signal in case of detecting a coincidence between a value of said carrier wave defining timer and said comparison value;
- a logical circuit set and reset according to said coincidence detecting signal;
- a transfer register for transferring said comparison value to said compare register at a predetermined timing;
- a one-shot timer set with said count value held in said reload register in synchronism with said set-reset of said logical circuit;
- means for generating said pulse width modulation signal according to an output signal of said one-shot timer and an output signal of said logical circuit.
Dependencies are inferred from the claim text.