Pseudo SRAM/CellularRAM ISSI Pseudo SRAM/CellularRAM Devices offer the best of both DRAM and SRAM features. ISSI PSRAM/CellularRAM has an SRAM-like architecture. Unlike DRAM, there is a hidden re-fresh feature that does not require a physical refresh. These CellularRAM devices are designed in accordance with the CellularRAM standards and are available in CRAM 1.5 and CRAM 2.0.