1. Field of the Invention
The present invention generally relates to a real time clock circuit having an internal clock generator. Specifically, the present invention relates to a set-top box having a single clock generator, which is internal to the real time clock circuit and is capable of generating multiple frequencies.
2. Related Art
Set-top boxes are becoming increasingly popular in many households. Specifically, set-top boxes are commonly used to receive cable and/or satellite television signals. As their popularity continues to grow, the functionality provided by the set-top boxes improves. For example, many of today's set-top boxes not only display date and time information, but also provide users with viewing schedules, pay per view options, etc. at the press of a button.
Unfortunately, the functionality provided by a set-top box must be balanced against its cost. Specifically, as the functional capabilities of a set-top box become more advanced, the quantity and cost of the components that must be incorporated increases. For example, many of today's set-top boxes are constructed using two (or more) clock oscillators. One clock oscillator generates a clock signal having a first speed (e.g., 27 MHz), while the second clock oscillator generates a clock signal having a second speed (e.g., 54 MHz). The clock oscillators each drive certain components within the set-top box. For example, in a typical set-top box one clock oscillator (externally) drives a real time clock (RTC) circuit, while another clock oscillator drives a device control register (DCR). Since each clock oscillator could cost several dollars, the inclusion of multiple clock oscillators can greatly effect the total cost of the set-top box.
Still yet, other existing real time clock macros make use of a precision oscillator input to accurately keep the correct time. Precision oscillators are generally used in devices such as personal computers where the information is set once and expected to remain accurate for many months or days. To this extent, precision oscillators are expensive and would considerably add to the cost of a set-top box.
In view of the foregoing, there exists a need to provide a set-top box that includes a single clock oscillator. To this extent, a need exists for a real time clock circuit within a set-top box to include the single clock generator as an internal component. A further need exists for the internal clock generator to receive a clock signal from an external clock oscillator and generate multiple signals therefrom. Still yet, a need exists for updates to the clock signal generated by the internal clock oscillator to be received from an external source such as a satellite or the like.