Semiconductor device for keyless entry transmitter

1. A semiconductor device for a keyless entry transmitter, the semiconductor device comprising:

a command data circuit connected to communication terminals for communication with a microcomputer;

a memory circuit connected to the command data circuit for storing rolling code data;

a timer period setting register connected to the command data circuit for storing timer period setting data;

a timer circuit connected to the command data circuit, the timer period setting register and a clock terminal for outputting an enable signal for placing the microcomputer into an intermittent operation state upon receiving an output signal of the command data circuit, an output signal of the timer period setting register, and a clock signal of the clock terminal;

a regulator output voltage setting register connected to the command data circuit for outputting a signal in response to an output signal of the command data circuit; and

a regulator circuit connected to the regulator output voltage setting register for outputting an output voltage upon receiving an input voltage and the output signal of the regulator output voltage setting register.

2. A semiconductor device for a keyless entry transmitter, the semiconductor device comprising:

a timer circuit for controlling an operation time of a wireless transmission circuit;

a regulator circuit for supplying power to the wireless transmission circuit, the regulator circuit having a memory, a data line and a clock line for communicating with the microcomputer, an output voltage of the regulator circuit being varied in accordance with data from the microcomputer;

a memory circuit for storing rolling code data; and

an enable terminal for outputting an enable signal for activating the microcomputer in accordance with a timetable controlled by the timer circuit, the enable signal being switchable between an active state and an inactive state to place the microcomputer in an intermittent operation state.

3. A semiconductor device for a keyless entry transmitter according to claim 2 ; wherein the timer circuit has a circuit communicating with the microcomputer for controlling the timetable to switch the enable signal of the timer circuit between an active state and an inactive state in response to data received from the microcomputer.

4. A semiconductor device for a keyless entry transmitter according to claim 3 ; wherein the timer circuit has a memory for storing data from the microcomputer.

5. A semiconductor device for a keyless entry transmitter according to claim 3 ; wherein the enable signal of the timer circuit alternates automatically between an active state and an inactive state.

6. A semiconductor device for a keyless entry transmitter according to claim 2 ; wherein the output voltage of the regulator circuit is varied in order to optimize a radio reaching range and power consumption of the wireless transmission circuit through adjustment of a level of a voltage supplied to the wireless transmission circuit.