n25q256 Numonyx, n25q256 Datasheet - Page 24

• 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

Operating features
5
5.1
5.1.1
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Operating features
Requirements for 256 Mb Address Space
When the memory size is 256Mb, memory needs to be addressed using a 32 bit address.
Therefore, one additional bit is necessary to addressability in N25Q256 respect 24 bit
address used to address memory size lower than 256Mb and bits A31'A25 are don't care.
The management of the added address bit will be implemented in two different ways:
3 Byte Address Mode (Segmentation)
The 256 Mb device includes an 8-bit volatile register to manage segmentations: it contains
the 4th byte address (A31 ' A24) to allow addressability beyond 128Mb when 3-byte
address mode is enabled.
Table 2.
A32 to A25 are Don’t Care. During EAR, reading these bits will read as 0. The default value
of bit <0> in EAR is 0; this value can be changed by NVCR bit.
Figure 7.
Erase/Program operations act in the selected segment, Bulk Erase instruction erases the
entire device, Read operations start in the selected 128Mbit, but they are not bounded in it:
when the last byte of the segment is reached, the next out byte (in a continuous reading) is
the first of the other segment so that download of the whole array is possible with one
instruction. The value in the EAR does not change when a read operation crosses the
selected 128Mbit boundary.
In 3-address byte modality, XiP is possible only in the selected segment.
A31
Bit 7
by means a segmentation of the array in two segments of 128Mbit each one, so that
user can choose the segment in which run a modify operation or start a reading
operation;
by means an additional address byte so that the total number of address bytes to be
specified directly by user is four.
A30
Extended Address Register (EAR)
Upper and Bottom 128 Bits
Bit 6
A29
Bit 5
A28
Bit 4
Micron Technology, Inc., reserves the right to change products or specifications without notice.
A27
Bit 3
A26
Bit 2
©2010 Micron Technology, Inc. All rights reserved.
A25
Bit 1
N25Q256 - 3 V
A24
Bit 0