The IS25LP064A 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 are 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 133MHz allow for equivalent clock rates of up to 532MHz (133MHz x 4) which equates to
66Mbytes/s of data throughput. The IS25xP series of Flash adds support for DTR (Double Transfer Rate)
commands that transfer addresses and read data on both edges of the clock. 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.
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.
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-volatile Quad Enable (QE) bit status in the Status
Register. Power Reset or Hardware/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
In addition to SPI and QPI features, the device also supports Fast READ DTR operation, which allows high data
throughput while running at lower clock frequencies. DTR READ mode uses both rising and falling edges of the
clock to drive output, resulting in reducing input and output cycles by half.