Overview The LC78624E is a CMOS LSI that implements the signal processing and servo control required by compact disc players. Including an EFM-PLL and text decoder, the LC78624E strictly limits functionality to basic signal processing and servo system operation to achieve the best cost-performance balance for low-end players. As basic functions, the LC78624E provides demodulation of the EFM signal from the optical pickup, de-interleaving, error detection and correction, and processes servo commands sent from the control microcontroller. Features • 64 pin QFP • 5 V single-voltage power supply Functions • Input signal processing: The LC78624E takes an HF signal as input, digitizes (slices) that signal at a precise level, converts that signal to an EFM signal, and generates a PLL clock with an average frequency of 4.3218 MHz by comparing the phases of that signal and an internal VCO. • Precise reference clock and necessary internal timing generation using an external 16.9344 MHz crystal oscillator • Disk motor speed control using a frame phase difference signal generated from the playback clock and the reference clock • Frame synchronization signal detection, protection and interpolation to assure stable data readout • EFM signal demodulation and conversion to 8-bit symbol data • Subcode data separation from the EFM demodulated signal and output of that data to an external microcontroller • Subcode Q signal output to a microcontroller over the serial I/O interface after performing a CRC error check (LSB first) • Serial output to a microcontroller via the text decoder of the song titles and other text data stored in the Subcode R through W channels of the read-in area • Demodulated EFM signal buffering in internal RAM to handle up to ±4 frames of disk rotational jitter • Demodulated EFM signal reordering in the prescribed order for data unscrambling and de-interleaving • Error detection, correction, and flag processing (error correction scheme: dual C1 plus dual C2 correction) • The LC78624E sets the C2 flags based on the C1 flags and a C2 check, and then performs signal interpolation or muting depending on the C2 flags. The interpolation circuit uses a dual-interpolation scheme. The previous value is held if the C2 flags indicate errors two or more times consecutively. • Support for command input from a microcontroller: commands include track jump, focus start, disk motor start/stop, muting on/off and track count (8 bit serial input) • Built-in digital output circuits. • Arbitrary track counting to support high-speed data access • Zero cross muting • Supports the implementation of a double-speed dubbing function. • Support for bilingual applications. • General-purpose I/O ports: 5 pins
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