Serial Quad I/O (SQI) Flash Memory
SST26VF016 / SST26VF032
Data Sheet
Device Operation
The SST26VF016/032 supports both Serial Peripheral Interface (SPI) bus protocol and the new 4-bit
multiplexed Serial Quad I/O (SQI) bus protocol. To provide backward compatibility to traditional SPI
Serial Flash devices, the device’s initial state after a power-on reset is SPI bus protocol supporting only
Read, High Speed Read, and JEDEC-ID Read instructions. A command instruction configures the
device to Serial Quad I/O bus protocol. The dataflow in this bus protocol is controlled with four multi-
plexed I/O signals, a chip enable (CE#), and serial clock (SCK).
SQI Flash Memory protocol supports both Mode 0 (0,0) and Mode 3 (1,1) bus operations. The differ-
ence between the two modes, as shown in Figures 4 and 5, is the state of the SCK signal when the
bus master is in Stand-by mode and no data is being transferred. The SCK signal is low for Mode 0
and SCK signal is high for Mode 3. For both modes, the Serial Data I/O (SIO[3:0]) is sampled at the ris-
ing edge of the SCK clock signal for input, and driven after the falling edge of the SCK clock signal for
output. The traditional SPI protocol uses separate input (SI) and output (SO) data signals as shown in
Figure 4. The SST26VF016/032 use four multiplexed signals, SIO[3:0], for both data in and data out,
as shown in Figure 5. This quadruples the traditional bus transfer speed at the same clock frequency,
without the need for more pins on the package.
CE#
MODE 3
MODE 0
MODE 3
MODE 0
SCK
SI
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
DON T CARE
MSB
HIGH IMPEDANCE
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
MSB
SO
1359 F03.0
Figure 4: SPI Protocol (Traditional 25 Serial SPI Device)
CE#
MODE 3
MODE 3
MODE 0
CLK
MODE 0
SIO(3:0)
C1 C0 A5 A4 A3 A2 A1 A0
H0 L0 H1 L1 H2 L2 H3 L3
MSB
X = Don’t Care or High Impediance
1409 F04.1
Figure 5: SQI Serial Quad I/O Protocol
©2010 Silicon Storage Technology, Inc.
S71359-05-000
06/10
6
SST [ SILICON STORAGE TECHNOLOGY, INC ]
