CYM1840

The CYM1840 is a high-performance 8-megabit static RAM module organized as 256K words by 32 bits. The CYM1840 is constructed from eight 256K x 4 SRAMs in SOJ packages mounted on an epoxy laminate substrate with pins. Four chip selects (CS₀, CS₁, CS₂, and CS₃) are used to independently enable the four bytes. Two write enables (WE₀ and WE₁) are used to independently write to either the upper or lower 16-bit word of RAM. Reading or writing can be executed on individual bytes or on any combination of multiple bytes through the proper use of selects and write enables.

Writing to each byte is accomplished when the appropriate chip select (CS) and write enable (WE) inputs of the CYM1840 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 A₁₇).

Reading the CYM1840 is accomplished by taking the chip selects (CS) LOW, while write enables (WE) remain 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).

The data input/output pins of the CYM1840 stay in the high-impedance state when write enables (WE) are LOW or the appropriate chip selects are HIGH.