SAA4955TJ

The SAA4955TJ is a 2949264-bit field memory designed for advanced TV applications such as 100/120 Hz TV, PALplus, PIP and 3D comb filter. The maximum storage depth is 245772 words ´ 12 bits. A FIFO operation with full word continuous read and write could be used as a data delay, for example. A FIFO operation with asynchronous read and write could be used as a data rate multiplier. Here the data of SAA4955TJ is written once, then read as many times as required without being overwritten by new data.

In addition to the FIFO operations, a random block access mode is accessible during the pointer reset operation. When this mode is enabled, reading and/or writing may begin at, or proceed from, the start address of any of the 6144 blocks. Each block is 40 words in length. Two or more SAA4955TJs can be cascaded to provide greater storage depth or a longer delay, without the need for additional circuitry.

The SAA4955TJ contains separate 12-bit wide serial ports for reading and writing. The ports are controlled and clocked separately, so asynchronous read and write operations are supported. Independent read and write clock rates are possible. Addressing is controlled by read and write address pointers. Before a controlled write operation can begin, the write pointer must be set to zero or to the beginning of a valid address block. Likewise, the read pointer must be set to zero or to the beginning of a valid address block before a controlled read operation can begin.