The Microchip Technology Inc. 23X256 are 256 Kbit
Serial SRAM devices. The memory is accessed via a
simple Serial Peripheral Interface (SPI) compatible
serial bus. The bus signals required are a clock input
(SCK) plus separate data in (SI) and data out (SO)
lines. Access to the device is controlled through a Chip
Select (CS) input.
Communication to the device can be paused via the
hold pin (HOLD). While the device is paused,
transitions on its inputs will be ignored, with the
exception of Chip Select, allowing the host to service
higher priority interrupts.
The 23X256 is available in standard packages
including 8-lead PDIP and SOIC, and advanced
packaging including 8-lead TSSOP.