Digitally Sampled, Non-Proportional Control Voltage-Frequency Oscilla- Tor
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Fig. 1 illustrates in block diagram form an accurate, inexpensive voltage-frequency oscillator (VFO) operating at multiple frequencies. Computing systems generally operate on non-return to zero (NRZ) data. This format is inefficient and/or impractical in data bus and magnetic media storage systems. The NRZ data is encoded into formats where the information is contained in pulse transitions. Bus systems frequently use MANCHESTER or DIFFERENTIAL MANCHESTER coding. Magnetic media systems use "run-length-limited" codes - frequency modulated (FM), modified FM (MFM), and 2/7 code. (Image Omitted) A common feature of these encoding schemes is that they require a phase-locked loop (PLL) to decode them back into NRZ data.