CYM1821

The CYM1821 is a high-performance 512-Kbit static RAM module organized as 16K words by 32 bits. The CYM1821 is constructed from eight 16K x 4 SRAM SOJ packages mounted on an epoxy laminate board with pins. Four chip selects (CS1, CS2, CS3, and CS4) are used to independently enable the four bytes. Reading or writing of the CYM1821 can be executed on individual bytes or any combination of multiple bytes through proper use of selects.

Writing to each byte is accomplished when the appropriate chip selects (CSN) and write enable (WE) inputs of the CYM1821 are both LOW. Data on the input/output pins (I/O_X) is written into the memory location specified on the address pins (A0 through A₁₃).

Reading theCYM1821 is accomplished by taking the chip selects (CSN) LOW, while write enable (WE) remains HIGH. Under these conditions the contents of the memory location specified on the address pins will appear on the data input/output pins (I/O_X).The data input/output pins stay in the high-impedance state when write enable (WE) is LOW, or the appropriate chip selects are HIGH.

Two pins (PD0 and PD1)of the CYM1821 are used to identify module memory density in applications where alternate versions of the JEDEC standard modules can be interchanged.