mirrorbit unused data lines an

mirrorbit unused data lines an
Connecting Unused Data Lines of
MirrorBit™ Flash
Application Note
By Wendy Kadlec
This document is intended to clarify how to properly treat unused data lines of MirrorBit Flash memory in a
system.
1. Organization Modes
Most Spansion MirrorBit Flash devices can support either x8 or x16 wide organization. The BYTE# pin
controls whether the device data I/O pins DQ15-DQ0 operate in the byte or word configuration. If the BYTE#
pin is set at logic '1', the device is in word configuration and DQ15-DQ0 are active. If the BYTE# pin is set at
logic '0', the device is in byte configuration, and only data I/O pins DQ7-DQ0 are active. The data I/O pins
DQ15-DQ8 are tri-stated.
2. Customer Applications
Typically, system designers select the byte mode memory configuration when only 8 data lines are required,
but it is acceptable to configure Flash devices in word mode and utilize only one byte portion of the 16-bit data
bus. For example, a system controller may have a 24-bit wide data bus. In order to support 24-bit wide bus,
the designer may choose to use two x16 Flash devices connected in a parallel fashion and configure both
devices in word mode. The first Flash is connected to the low word lane, DQ15-DQ0, and the second flash is
connected to the high word lane, DQ23 to DQ16 (Figure 2.1). To address the 24-bit wide flash memory
space, the processor would issue software commands to provide the required addresses to the flash devices
as needed.
Publication Number mirrorbit_unused_data_lines_an
Revision 01
Issue Date November 14, 2006
A pplication
Note
Figure 2.1 Processor Connected to Two Word Mode x8/x16 Flash on a 24-bit Wide Bus
PD15
PD14
PD13
PD12
PD11
PD10
PD9
PD8
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
DQ15/A-1
DQ14
DQ13
DQ12
DQ11
DQ10
DQ9
DQ8
DQ7
DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
Processor
100K
PD23
PD22
PD21
PD20
PD19
PD18
PD17
PD16
DQ15/A-1
DQ14
DQ13
DQ12
DQ11
DQ10
DQ9
DQ8
DQ7
DQ6
DQ5
DQ4
DQ3
DQ2
DQ1
DQ0
Flash
Flash
Note that on Figure 2.1 the unused data pins on the Flash device of the upper word lane are pulled-down to
ground through an external resistor (100 KΩ is recommended). Handling unused data lines in this matter is
necessary for successful write buffer programming.
The Write buffer programming capability was introduced to MirrorBit based Flash by Spansion. This capability
allows the system to write 16 words (GL-A and GL-N family) in one programming operation. This results in
faster effective programming time than the standard programming algorithms. Please refer to specific
Spansion MirrorBit Flash data sheet for detailed information on the write buffer program command sequence
of a device.
When a Flash device is configured as x16 or word mode, as in this design example, data I/O pins DQ15-DQ0
become active signals. During a write buffer programming operation, in the fourth cycle of write-to-buffer
command, DQ15-DQ0 data bits are used to set appropriate word count (WC). Since maximum word count is
16 words for devices in the both the GL-A and GL-N family, data bits DQ15-DQ4 have to be logic '0' to set the
correct word count (WC) value.
In this particular example (Figure 2.1), if the upper unused data bits were tied externally to power instead of
ground, it would inadvertently set DQ15-DQ8 data lines to logic '1' and lead to an illegal word count (WC)
during a write-to-buffer command sequence. As a result, the write buffer programming command would fail to
complete.
3. Conclusion
When using a Spansion MirrorBit flash device, unused data lines need to be treated appropriately to ensure
successful write buffer programming. It is recommended that unused data lines be tied to ground through an
external 100 KΩ resistor so that the write buffer word count value is valid.
2
Connecting Unused Data Lines of MirrorBit™ Flash
mirrorbit_unused_data_lines_an_01 November 14, 2006
App l ic atio n
4.
No t e
Revision History
Section
Description
Revision 01 (November 14, 2006)
Initial release
Colophon
The products described in this document are designed, developed and manufactured as contemplated for general use, including without
limitation, ordinary industrial use, general office use, personal use, and household use, but are not designed, developed and manufactured as
contemplated (1) for any use that includes fatal risks or dangers that, unless extremely high safety is secured, could have a serious effect to the
public, and could lead directly to death, personal injury, severe physical damage or other loss (i.e., nuclear reaction control in nuclear facility,
aircraft flight control, air traffic control, mass transport control, medical life support system, missile launch control in weapon system), or (2) for
any use where chance of failure is intolerable (i.e., submersible repeater and artificial satellite). Please note that Spansion will not be liable to
you and/or any third party for any claims or damages arising in connection with above-mentioned uses of the products. Any semiconductor
devices have an inherent chance of failure. You must protect against injury, damage or loss from such failures by incorporating safety design
measures into your facility and equipment such as redundancy, fire protection, and prevention of over-current levels and other abnormal
operating conditions. If any products described in this document represent goods or technologies subject to certain restrictions on export under
the Foreign Exchange and Foreign Trade Law of Japan, the US Export Administration Regulations or the applicable laws of any other country,
the prior authorization by the respective government entity will be required for export of those products.
Trademarks and Notice
The contents of this document are subject to change without notice. This document may contain information on a Spansion product under
development by Spansion. Spansion reserves the right to change or discontinue work on any product without notice. The information in this
document is provided as is without warranty or guarantee of any kind as to its accuracy, completeness, operability, fitness for particular purpose,
merchantability, non-infringement of third-party rights, or any other warranty, express, implied, or statutory. Spansion assumes no liability for any
damages of any kind arising out of the use of the information in this document.
Copyright © 2006 Spansion Inc. All Rights Reserved. Spansion, the Spansion logo, MirrorBit, ORNAND, HD-SIM, and combinations thereof are
trademarks of Spansion Inc. Other names are for informational purposes only and may be trademarks of their respective owners.
November 14, 2006 mirrorbit_unused_data_lines_an_01
Connecting Unused Data Lines of MirrorBit™ Flash
3
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