High Density Serial Flash Addressing

APPLICATION NOTE
Macronix High Density Serial Flash Addressing
1. Introduction
Many consumer products have converted or are converting from parallel flash to SPI serial flash.
Generally, high end applications require higher memory density, but in the past, serial flash densities
were limited to 128Mb due to addressing constraints. Macronix offers high density serial flash
products with several different solutions to the previous 128Mb limitation. This application note will
discuss the 128Mb addressing limitation and Macronix solutions to addressing 256Mb and above.
The information in this document is based on datasheets listed in Section 5. Newer versions of the
datasheets may override the contents of this document.
2. 128Mb Memory Address Limitation
In general, the serial flash command protocol (Figure 2-1) uses a 1-Byte instruction opcode followed
by a 3-Byte (24-bit) address. However, 3 bytes of address is only sufficient to define an address range
of zero to 16MBytes (0 to 128Mb). In order to access flash above 128Mb, the address length needs to
be extended to 4 bytes (32-bits) or use a 128Mb stacked die solution utilizing two CS# pins to select
the top or bottom die.
Figure 2-1: 3-Byte Address Mapping Range
P/N: AN0209
1
Ver: 01, Dec. 17, 2012
APPLICATION NOTE
Macronix High Density Serial Flash Addressing
3. Macronix’s Solutions to Access Memory ≥256Mb
Macronix provides products with several different solutions that enable full access to flash densities of
256Mb and larger. Table 3-1 shows access solutions and the 256Mb 3V products that support them.
Please refer to the Macronix website for other densities and voltage options.
Table 3-1: Macronix 256Mb Product List
Access Solution
Enter 4-Byte Address Mode
Extended Address Register (EAR)
4-Byte Address Command Set
Default 4-Byte Address Mode
Two CS# Pins (to control two
stacked 128Mb flash)
MX25L25635F
MX25L25639F
Yes
Yes
Yes
-
MX25L25735F
MX25L25835E
Yes
-
-
Yes
-
3.1 Solution #1: Enter 4-Byte Address Mode
This solution requires the system to use an address-enhanced SPI protocol by adding a 4th address
byte to all serial flash commands that normally use 3-Byte addresses. The device defaults to 3-Byte
address mode, and 4-Byte mode is enabled with the EN4B command (0xB7). In 4-Byte mode, the
legacy command set is still used*1, but 4-Bytes of address, instead of three, are sent during the
address phase. The 4-Byte and 3-Byte address modes are mutually exclusive and only one can be
active at a time. The EX4B command (0xE9) is used for exiting 4-Byte address mode. As shown in
Figure 3-1, the device will also return to the default 3-Byte address mode after a power cycle,
hardware reset, or software reset. The active address mode of the MX25L25635F and MX25L25639F
can be determined by reading the Configuration Register and checking the “4BYTE” bit (Bit5 in Table
3-2). If it is set to ‘1’, then 4-Byte address mode is active. Otherwise, 3-Byte address mode is active.
Note:
1. The number of address bytes in the following commands is independent of the 3-Byte and 4-Byte Address
modes: 4READ for top 128Mb (0xEA), RDSFDP, RES and REMS.
Figure 3-1: 3-Byte Address to 4-Byte Address Flow of MX25L25635F
Power on or
Reset
3-byte address
mode
EN4B (0xB7)
command
4-byte address
mode
EX4B (0xE9)
command
Table 3-2: Configuration Register (MX25L25635F and MX25L25639F)
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
DC1
DC0
Dummy cycle
P/N: AN0209
4BYTE
1=4-byte address
mode (Default=0)
Reserved
TB
1=bottom
area protect
2
Bit0
OSD2
OSD1
OSD0
Output driver strength
Ver: 01, Dec. 17, 2012
APPLICATION NOTE
Macronix High Density Serial Flash Addressing
3.2 Solution #2: Extended Address Register (EAR)
If the system only supports 3-Byte addressing, the Extended Address Register mode is an alternative
method that can be used to access memory beyond the 128Mb limit. The device provides a volatile
8-bit EAR register that is automatically appended to the normal 3-Byte address and in effect creates a
4-Byte address*1. No commands are needed to enter or exit this mode. EAR mode operates with the
legacy 3-Byte address command set.
As shown in Table 3-3, Bits[7:0] of the EAR correspond to address bits A[31:24] and must be loaded
prior to its usage. The default value of the EAR is 0x00 and the standard 3-Byte address maps directly
to the lower 128Mb of memory. An EAR value of 0x01 would remap a 3-Byte address into the upper
128Mb of memory. The usage model is as follows: system issues the Write Extended Address
Register instruction (0xC5) with a register value used to set or clear EAR[0]. When cleared to ‘0’, the
bottom 128Mb memory can be accessed. When set to ‘1’, the top 128Mb memory can be accessed.
The system should check the EAR value before using it to access flash memory. This is done by
using the Read Extended Address Register instruction (0xC8) and reading the 8-Bit EAR value.
The EAR supplies the higher address bits to form the starting address for read operations, but the
EAR setting does not limit the read operation to the bottom or top 128Mb. For example, a read
operation that begins in the lower 128Mb is free to continue reading into the upper 128Mb. Likewise a
read operation that begins in the upper 128Mb is free to read to the end of memory and wrap around
and continue reading into the lower 128Mb.
Note:
1. When device is commanded to enter 4-byte address mode, the EAR[7:0] becomes “Don’t Care” for all
commands using 4-Byte addresses.
.
Table 3-3: Extend Address Register
Bit7
Bit6
Bit5
Bit4
Bit3
A31
Bit2
A30
A29
A28
A27
A26
Reserved flash densities great than 256Mb
Bit1
Bit0
A25
A24
256Mb
Figure 3-2: Top and Bottom 128M bits
P/N: AN0209
3
Ver: 01, Dec. 17, 2012
APPLICATION NOTE
Macronix High Density Serial Flash Addressing
3.3 Solution #3: 4-Byte Address Command Set
This solution uses an alternate 4-Byte address command set (Table 3-4) that supplements the legacy
3-Byte address command set. Both command sets are always available and the system may choose
which set to use. The operation of the 4-byte address command set is similar to the original 3-byte
address command set with the only difference being 4-byte address commands require 4-Bytes of
address (A31-A0) following the instruction opcode. The 4-Byte address command set eliminates the
need to enter or exit 4-Byte addressing mode.
Table 3-4: 4 Byte Address Command Set
Command Set
READ4B
FASTREAD4B
2READ4B
DREAD4B
4READ4B
QREAD4B
Instruction Opcode
Address Bytes
13 (Hex)
4
Normal
Read
0C (Hex)
4
Single I/O Fast
Read
BC (Hex)
4
Dual I/O
Fast Read
3C (Hex)
4
Dual Output
Fast Read
EC (Hex)
4
Quad I/O
Fast Read
6C (Hex)
4
Quad Output
Fast Read
Command Set
PP4B
4PP4B
BE4B
BE32K4B
SE4B
Instruction Opcode
Address Bytes
12 (Hex)
4
Action
Page Program
3E (Hex)
4
Quad Input
Page Program
DC (Hex)
4
Block Erase
(64KB)
5C (Hex)
4
Block Erase
(32KB)
21 (Hex)
4
Sector Erase
(4KB)
Action
3.4 Solution #4: Default 4-byte Address mode
Macronix offers the MX25L25735F which defaults to 4-Byte address mode. The 4-Byte address mode
is hardwired and no command or power cycle can change it to 3-Byte address mode. The
MX25L25735F uses the legacy 3-Byte command set, but always requires 4-Bytes of address instead
of 3-Bytes. The MX25L25735F does not use the 4-Byte address command set described in section
3.3.
P/N: AN0209
4
Ver: 01, Dec. 17, 2012
APPLICATION NOTE
Macronix High Density Serial Flash Addressing
3.5 Solution #5: 2x128Mb Devices Controlled By Two CS# Pins
The MX25L25835E is a 256Mb flash device built with two stacked 128Mb flash chips in the same
package (shown in Figure 3-2). Two external CS# pins are used to select which of the two stacked die
should be active. From the system’s point of view, the device behaves like two independent 128Mb
flash controlled by two independent CS# pins. It is up to the system to make sure that both CS#1 and
CS#2 are not asserted simultaneously as a bus conflict will occur on the data lines. The
MX25L25835E uses the legacy command set in 3-Byte address mode.
Figure 3-2: 2 CS# Pin Block Diagram
4. Summary
Macronix offers high density serial flash with a variety of solutions designed to solve the
128Mb address limitation. The user may refer to this application note to select a device
appropriate for the addressing capabilities of their application.
P/N: AN0209
5
Ver: 01, Dec. 17, 2012
APPLICATION NOTE
Macronix High Density Serial Flash Addressing
5. Reference
Table 5-1 shows the datasheet versions used for comparison in this application note. For the most
current, detailed specification, please refer to the Macronix Website at http://www.macronix.com
Table 5-1: Datasheet Version
Data sheet
Location
MX25L25635F
MX25L25639F
MX25L25735F
MX25L25835E
Website
Website
Website
Website
Date Issue
Revision
AUG. 07, 2012
SEP. 05, 2012
JUL. 18, 2012
NOV. 29, 2011
Rev. 0.02
Rev. 0.01
Rev. 0.00
Rev. 1.0
6. Revision History
P/N: AN0209
Revision
Description
Date
1.0
Initial Release
Dec. 17, 2012
6
Ver: 01, Dec. 17, 2012
APPLICATION NOTE
Macronix High Density Serial Flash Addressing
Except for customized products which have been expressly identified in the applicable agreement,
Macronix's products are designed, developed, and/or manufactured for ordinary business, industrial,
personal, and/or household applications only, and not for use in any applications which may, directly
or indirectly, cause death, personal injury, or severe property damages. In the event Macronix
products are used in contradicted to their target usage above, the buyer shall take any and all actions
to ensure said Macronix's product qualified for its actual use in accordance with the applicable laws
and regulations; and Macronix as well as it’s suppliers and/or distributors shall be released from any
and all liability arisen therefrom.
Copyright© Macronix International Co., Ltd. 2011~2012. All rights reserved, including the trademarks
and tradename thereof, such as Macronix, MXIC, MXIC Logo, MX Logo, Integrated Solutions Provider,
NBit, Nbit, NBiit, Macronix NBit, eLiteFlash, HybridNVM, HybridFlash, XtraROM, Phines, KH Logo,
BE-SONOS, KSMC, Kingtech, MXSMIO, Macronix vEE, Macronix MAP, Rich Au-dio, Rich Book, Rich
TV, and FitCAM. The names and brands of third party referred thereto (if any) are for identification
purposes only
For the contact and order information, please visit Macronix’s Web site at: http://www.macronix.com
P/N: AN0209
7
Ver: 01, Dec. 17, 2012