1 Mbit parallel SRAM for 5 V legacy buses
The CY62128BLL-55ZRIT is a 1 Mbit asynchronous SRAM from Infineon's MoBL® series, organized as 128K x 8 bits with a 55 ns access time.
55 ns access and 5 V supply — what they mean for the bus
The 55 ns access time sets the read-cycle floor: the processor must stretch its bus wait states to accommodate this window. On a 20 MHz bus (50 ns cycle), one wait state covers the access; at 25 MHz (40 ns cycle), two wait states are needed unless the memory controller supports a variable latency. The part draws its specified standby and active current at the nominal 5 V level; a drop to 4.5 V increases access time slightly but stays within the 55 ns max over the full temperature range. Asynchronous interface means no clock is needed — the chip select and output enable gates the data onto the bus directly. This simplifies the PCB layout compared to synchronous SRAM, but the address hold time relative to chip select must still meet the 55 ns write-cycle spec.
The 0.50 mm pin pitch and exposed pad require a solder-paste stencil aperture sized per the datasheet land pattern to avoid bridging during reflow.