n25q256 Numonyx, n25q256 Datasheet - Page 19

• Manufacturer Part Number: n25q256
• Description: 256-mbit 3 V, Multiple I/o, 4-kbyte Subsector Erase, Xip Enabled, Serial Flash Memory With 108 Mhz Spi Bus Interface
• Manufacturer: Numonyx

N25Q256 - 3 V
3
SPI Modes
These devices can be driven by a micro controller with its SPI peripheral running in either of
the two following modes:
CPOL=0, CPHA=0
CPOL=1, CPHA=1
For these two modes, input data is latched in on the rising edge of Serial Clock (C), and
output data is available from the falling edge of Serial Clock (C).
The difference between the two modes, as shown in
bus master is in standby mode and not transferring data:
C remains at 0 for (CPOL=0, CPHA=0)
C remains at 1 for (CPOL=1, CPHA=1)
Figure 5.
Shown here is an example of three devices working in Extended SPI protocol for simplicity
connected to an MCU, on an SPI bus. Only one device is selected at a time, so only one
device drives the serial data output (DQ1) line at a time; the other devices are high
impedance. Resistors R ensures that the N25Q256 is not selected if the bus master leaves
the S line in the high impedance state. As the bus master may enter a state where all
inputs/outputs are in high impedance at the same time (for example, when the bus master is
reset), the clock line (C) must be connected to an external pull-down resistor so that, when
all inputs/outputs become high impedance, the S line is pulled High while the C line is pulled
Low. This ensures that S and C do not become High at the same time, and so that the t
requirement is met. The typical value of R is 100 kΩ, assuming that the time constant R*C
CS3
SPI interface with
(CPOL, CPHA) =
SPI Bus Master
(0, 0) or (1, 1)
CS2 CS1
Bus master and memory devices on the SPI bus
SDO
SDI
SCK
R
R
C
S
SPI memory
DQ1DQ0
device
W
Micron Technology, Inc., reserves the right to change products or specifications without notice.
V
CC
HOLD
V
R
SS
C
S
Figure
DQ1 DQ0
SPI memory
device
W
5, is the clock polarity when the
V
HOLD
CC
©2010 Micron Technology, Inc. All rights reserved.
R
V
SS
C
S
DQ1DQ0
SPI memory
device
SPI Modes
W
V
CC
HOLD
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SHCH
V
V
V
SS
CC
SS
p