Abstract: A closed-caption decoder which uses separate clock generators to produce the sampling frequencies for the clock run-in signal and the data portion of the closed-caption signal. Each of the clock generators generates its signal from a common 12 MHz reference clock signal. The timing of the sampling clock signal for the closed-caption data is advanced at the start of the sampling interval to reduce the total timing errors in the sampling of the closed-caption data. Additionally, the decoder can adaptively select one of four edges of the clock run-in signal to use as its synchronizing reference. Furthermore, the decoder may be adapted to recognize more than one start byte pattern.

Abstract: A multi-port memory cell utilizes a storage cell to define complementary data storage nodes. Each read port of the memory cell includes two FETs respectively coupled between one of a pair of complementary data-out lines and a read enable line to isolate the read ports. Each of the gates of the two read port FETs is connected to one of the corresponding data storage nodes. The storage cell is read by pulling current from the read enable line and monitoring the difference between the complementary data-out lines.