概觀
The IS25LP/WP040E/020E/010E/512E/025E and Serial Flash memory offers a versatile storage solution with high
flexibility and performance in a simplified pin count package. ISSI’s “Industry Standard Serial Interface” Flash is
for systems that require limited space, a low pin count, and low power consumption. The device is accessed
through a 4-wire SPI Interface consisting of a Serial Data Input (SI), Serial Data Output (SO), Serial Clock (SCK),
and Chip Enable (CE#) pins, which can also be configured to serve as multi-I/O (see pin descriptions).
The device supports Dual and Quad I/O as well as standard, Dual Output, and Quad Output SPI. Clock frequencies
of up to 104MHz allow for equivalent clock rates of up to 416MHz (104MHz x 4) which equates to 52Mbytes/s of
data throughput. These transfer rates can outperform 16-bit Parallel Flash memories allowing for efficient memory
access to support XIP (execute in place) operation.
The memory array is organized into programmable pages of 256-bytes. This family supports page program mode
where 1 to 256 bytes of data are programmed in a single command. QPI (Quad Peripheral Interface) supports 2-
cycle instruction further reducing instruction times. Pages can be erased in groups of 4Kbyte sectors, 32Kbyte
blocks, 64Kbyte blocks, and/or the entire chip. The uniform sector and block architecture allows for a high degree
of flexibility so that the device can be utilized for a broad variety of applications requiring solid data retention.
GLOSSARY
Standard SPI
In this operation, a 4-wire SPI Interface is utilized, consisting of Serial Data Input (SI), Serial Data Output (SO),
Serial Clock (SCK), and Chip Enable (CE#) pins. Instructions are sent via the SI pin to encode instructions,
addresses, or input data to the device on the rising edge of SCK. The SO pin is used to read data or to check the
status of the device. This device supports SPI bus operation modes (0, 0) and (1, 1).
Multi I/O SPI
Multi-I/O operation utilizes an enhanced SPI protocol to allow the device to function with Dual Output, Dual Input
and Output, Quad Output, and Quad Input and Output capability. Executing these instructions through SPI mode
will achieve double or quadruple the transfer bandwidth for READ and PROGRAM operations.
QPI
The device supports Quad Peripheral Interface (QPI) operations only when the device is switched from
Standard/Dual/Quad SPI mode to QPI mode using the enter QPI (35h) instruction. The typical SPI protocol requires
that the byte-long instruction code being shifted into the device only via SI pin in eight serial clocks. The QPI mode
utilizes all four I/O pins to input the instruction code thus requiring only two serial clocks. This can significantly
reduce the SPI instruction overhead and improve system performance. Only QPI mode or SPI/Dual/Quad mode
can be active at any given time. Enter QPI (35h) and Exit QPI (F5h) instructions are used to switch between these
two modes, regardless of the non-volatible Quad Enable (QE) bit status in the Status Register. Power Reset or
Software Reset will return the device into the standard SPI mode. SI and SO pins become bidirectional I/O0 and
I/O1, and WP# and HOLD# pins become I/O2 and I/O3 respectively during QPI mode.