CYM7232

The CYM7232 and the CYM7264 consist of a full-function DRAM controller and a pipelined/FIFO data multiplexer/demultiplexer with error correction for cache-based, uniprocessor, and multiprocessor systems memory control. The CYM7232 performs 32-bit Error Detection and Correction (EDC) while CYM7264 performs 64-bit EDC. They both connect to the system bus through a 64-bit-wide data bus, and a 36-bit wide address bus. The CYM7232 also supports 32-bit system buses. The bus transfer control signals support i486, Pentium, i860, 68040, 88110, SPARC MBus, MIPS R4000, or other interfaces. The controller module interfaces to the DRAM array through a 16-byte-wide data bus plus check bits, a 12-bit row/column address bus, four RAS outputs, four CAS outputs, and four read/write control lines.

During write operations, data passes from the system bus through a FIFO array that acts as an incoming queue. Writes occur at the system bus speed until the  CYM1946's FIFO is full (sixteen 64-bit words). The FIFO supports cache-line copy-back and fill operations, reducing system bus traffic to a minimum. The module supports posted writes, by suspending the actual write to DRAM until the cache-line read is completed during cache-line write-back. This speeds cache-line fill operations.

The  CYM1946's pipelines a 16-byte-wide DRAM access into the data path for EDC, and multiplexes the data to the system bus during reads. This supports high-speed burst line fills with error corrected data. Reads and writes may be inhibited for multiprocessor support. Inhibited reads may be turned into reflective reads, and inhibited writes may be turned into reads-for-ownership.