NOR Flash FAQs - KBA222273

Version 20

    Version: *H

    1. Does the sector or chip erase time increase with the age of the device?
    The sector or chip erase time does not increase with age of the device, but may increase as the number of erase and program cycles increase.

    2. What is pre-programming during erase?
    During the sector or chip erase operation, pre-program refers to the operation of checking the existing data bits and programming any bits from the ‘1’ (erase) state to the ‘0’ (program) state. When pre-programming is completed, all data bits within the memory array are pre-programmed to ‘0’; then the (Sector or Chip) Erase algorithm initiates, erasing all bits from the ‘0’ (program) state to the ‘1’ (erase) state. Flash memory can only be programmed from ‘1’ to ‘0’. However, flash memory can only be (sector or chip) erased from ‘0’ to ‘1’ all at once for each sector or entire memory array. Within the sector or chip erase operation, the pre-program algorithm is initiated automatically, transparent to the user, and cannot be disabled.

    3. Why do some Cypress datasheets mention "not including 00h program before erasure"?
    It means that the pre-program time is not included in the erase time. For products without this remark, pre-program time is included in the erase time in the datasheet specification.

    4. Is the write period (maximum value) in write buffer mode dependent on the number of write words?

    No. Although a flash memory device can support both single-word programming and write-buffer programming, the preferred method is write-buffer programming because it is more efficient.  However, it is recommended to load the buffer with the maximum number of words, because the write buffer time is the same whether one word or maximum words are loaded in the buffer.  Therefore, the write buffer programming time does not depend on the number of words.

    5. Is it okay to keep the Byte pin open?
    Do not leave the Byte pin open. Input VIL when in x8 mode, and VIH when in x16 mode. Because the GL-T series has an internal pull-up, it can be OPEN when used in x16 mode.

    6. How can I connect byte access (DQ15/A-1 pin to DQ14-8)?
    During BYTE mode access, the DQ15 pin is assigned as A-1, the least significant bit (LSb) of the address bus. Therefore, connect the A-1 pin to the lowest address A0 of the CPU. DQ14-8 will be tri-stated (HI-Z) and can be left OPEN/floating. The BYTE# pin should be set ‘0’ (LOW).

    7. Is it okay to leave the NC pin open? Is it safe to connect the NC pin to power supply and signal wires?
    Yes, NC pin can be open. The NC pin is the No Connect pin. There is no internal physical or electrical connection from the die to the lead frame. It is safe to connect the NC pin with power supply or signal wires.

    8. What is the maximum operating junction temperature of the device?
    You can obtain the junction temperature (Tj) from the following calculation.


    Tj (θja × Pd) Ta

    θja ( / W)    : Thermal resistance between junction temperature (Tj) and ambient temperature (Ta)
    Pd (W)            : Power consumption = Operating voltage (Vd max) × Operating current (Id max)
    Ta ()            : Ambient temperature

    Calculation example:
    Type: S29GL256N90TFIR20H

    Calculation condition:
    ja 44 ( / W)
    TSOP56 package, using thermal resistance value in no wind· Pd 0.18 (W)
    Use maximum power consumption (when program / erase) · Ta 85 () [Use maximum operating temperature]

    Calculation result:
    Tj = (44 x 0.18) + 85 = 92.92 ()

    9. The datasheet mentions that data retention of the flash device is 20 years typ. From which point does this duration count?
    Data retention of typ 20 years is the number of years from the last write on the flash. Data retention is dependent on the number of Program/Erase cycle, system field temperature, and cycling interval time. Contact Cypress for the guaranteed value of Program/Erase cycle and data retention.

    10. What are the factors that affect the data retention lifetime of the product after Program/Erase cycling?

    Data retention after Program/Erase cycling is determined by three main parameters:

    1. System Field Temperature (Program/Erase Cycling and Data Storage)
    2. Total number of Program/Erase Cycles
    3. Cycling Interval Time

    For more information on Endurance and Data Retention Characterization of Cypress Flash Memory, see AN217979.

    11. What is the meaning of DDR in SPI Flash?
    Double Date Rate (DDR) means that data can be taken on the rising and falling edges of CLK, and the data transfer speed is twice the SDR at the same CLK frequency. Cypress' FL-S, FS-S, and FL-L series support DDR features.

    12. The datasheet shows that data retention after 10K Program/Erase and 100K Program/Erase cycles is 20 years and 2 years, respectively. What is the average field temperature for these values?
    Generally, the assumption is 55 °C average temperature for data retention according to JEDEC.

    13. What is the difference between S25FL127S and S25FL128S with the same density?
    FL127S is a product developed mainly for small packaging by eliminating less requested functions and adjusting its performance. For applications that require the full feature set and higher performance, such as DDR, Vio, faster program/erase timing, and so on, it is strongly recommended that you consider S25FL128S.


    14. What are the differences in performance between GL-T and GL-S families?
    The read performance of the GL-T family is the same as the GL-S for the respective densities. GL-S provides a high program performance of 1.5 MBps and an erase performance of 0.477 MBps compared to 1.14 MBps and 0.245 MBps, respectively, for GL-T. See AN202453 - Migration From GL-P and GL-S to GL-T Flash for the differences between GL-T and GL-S families

    15. What is the advantage of S25FL-S over the S25FL-L family devices?
    The S25FL-S family features a double-data-rate (DDR) frequency of 80 MHz compared to 66 MHz for the S25FL-L family. The S25FL-S family is, therefore, better suited for applications that require a very fast read bandwidth such as clusters and infotainment.

    16. What is the advantage of the S25FL-L family devices over the S25FL-S family devices?
    The S25FL-L family features a uniform 4-KB sector architecture, whereas the S25FL-S family features 64-KB hybrid sectors and 256-KB uniform sectors. With the hybrid sector architecture, the device has a limited number of 4-KB sectors; the remaining sectors can be of 64 KB in size. The uniform 4-KB sector architecture provides greater flexibility than the hybrid sector architecture because it allows for finer granularity when programming and updating data.

    Figure 1. FL-L Sector Structure

    17. How do I reprogram the Non-volatile Configuration Register (NVCR)?
    After issuing the WREN command (06h), enter the WRR (01h) command. After entering the WRR command, the device will automatically erase the register value; then it programs the new value in a single operation.

    For details, see the 'Write Register (WRR 01h)’ section in the device datasheet.

    18. What is the recommended land pattern for S25FL-P, S70FL-P, S25FL-S, S70FL-S, S25FS-S, and S70FS-S family devices?
    See the application note, AN98508 - Cypress Serial Peripheral Interface (SPI) FL Flash Layout Guide.

    19. Is it better to connect the WP#/ACC pin to a pull-up resistor when it is not used?
    The WP#/ACC pin has an internal pull-up resistor, so you can leave it open.

    20. For Power-On Reset of S25FL1-K, if VCC drop between VCC (Min) and VCC (Low), when VCC returns, is there any problem in flash operation?
    If VCC drops between VCC (min) and VCC (low) but stays above VWI, it is considered power on and will work correctly when VCC returns to the normal operating range. However, if VCC drops below VWI, you need to perform POR: for this, VCC must drop below VCC (low) for tPD period and meet the tVSL and tPUW parameters when VCC returns to the normal operating range.

    Figure 2. Power-up Timing Diagram

    Figure 3. Power-Down Timing Diagram

    21. What is the difference between the lowest sector protected and the highest sector protected model?
    The difference between the two models is that the protected sectors differ when WP # ACC = VIL. For the ‘High Protect’ model, the end sector will be protected. For the ‘Low Protect’ model, Sector#0 will be protected. In term of applications, there is no difference between the two models.

    22. What is Cypress' closest suggested migration path from Micron's N25Q SPI NOR Flash?
    Cypress' closest suggested migration path from N25Q is S25FL-L/S25FL-S. These may not be a direct drop-in replacement. You may need to analyze specific situations to find out the possibility of migration. See the application note, AN202471 - Migrating to Cypress S25FL-L Serial NOR Flash from Winbond W25Q-JV/FV, Micron N25Q-A, and Macronix M25L-F Devices.

    23. What is Cypress' closest suggested migration path from Micron's MT25QU SPI NOR Flash?
    Cypress' closest suggested migration path from MT25QU is S25FS-S. These may not be a direct drop-in replacement. You may need to analyze specific situations to find out the possibility of migration.

    24. What is Cypress' closest suggested migration path from Micron's M29W/M29EW Parallel NOR Flash?
    Cypress' closest suggested migration path from M29W/M29EW is S29GL-S. These may not be a direct drop-in replacement. You may need to analyze specific situations to find out the possibility of migration.


    25. What is Cypress' closest suggested migration path from Numonyx P33 Parallel NOR Flash?
    Cypress' closest suggested migration path from Numonyx P33 is S29GL-S. These may not be a direct drop-in replacement. You may need to analyze specific situations to find out the possibility of migration.  See the application note, AN98584 - Migration from Numonyx™ P33 to Cypress S29GL-S.

    26. In operating state of S29GL-S, if its temperature exceeds Ta=85, will it lead to destruction immediately?
    Although the device will work even if it exceeds the recommended operating temperature, Cypress does not guarantee it will not cause malfunction. Also, if it exceeds its absolute maximum spec, there is a possibility of erratic operation occurring. It is essential that the device operates in its recommended operating range.

    27. Since there is no DPD (Deep Power Down Mode) in FL-S, is there any similar function to this mode?
    S25FL-S does not support any function similar to the Deep Power Down mode. Standby Power mode is the lowest power mode that consumes the lowest current. S25FL-S will enter Standby Mode and will consume ~70 µA, but it is ready to accept any command. Once the CE# input signal goes LOW, the SPI flash memory device will consume a maximum of ~100 mA.

    28. What is the advantage of using the Write Buffer Program operation in GL series?
    Each Write Buffer Program operation allows for programming of 1 bit up to 256 bytes/512 bytes. This results in faster and more effective programming time than the standard programming algorithms. Figure 4 explains how the Write Buffer Program operation in GL series devices can improve the device programming performance compared to the Single Word Programming operation.

    Figure 4. Programming 256 Words to Flash

    29. Some distributor part number has extra suffix. For example, S29AL016D70BFI020 with extra suffix E or (E). What does "E" mean?

    The extra suffix was earlier used by erstwhile Spansion to represent the Fab/Assy location. After the acquisition of Spansion by Cypress, a different format is used. Create a Technical Support case to obtain the specific Fab/Assy location.


    30. Can I connect the RFU pin to VDD or GND?

    RFU means Reserved for Future Use. There is no problem if you connect the RFU pin to VDD or GND; however, in future, if Cypress assigns a functionality to the pin, and introduces the pin as a new part, you might face issues in migrating to the new part. Generally, Cypress recommends that you leave the RFU pin floating.


    31. Is it possible to write a single byte at a time in FL-S series?

    For this device, writing a single byte at a time is possible if the sector is blank or erased, but it is not efficient. This is because writing a single byte at a time takes the same amount of time to write one full page in one operation using Page Programming Buffer. However, Single Byte Programming disables ECC on the second single-byte program to the same 16-byte ECC unit. It is always recommended to use Page Programming Buffer for effective programming.


    32. How does word programming with Multiple Word Burst Data Load operation work in S26KL-S/S26KS-S?

    The burst write for the word programming sequence is a single HyperBus™ transaction. It starts with CS# falling edge, followed by the burst writes (two unlock cycles, followed by the A0h command, followed by up to 256 address/data pairs), followed by CS# rising edge to terminate the transaction. In this case, a flash command is not required to initiate the programming operation; the CS# rising edge initiates the programming.


    33. Will word programming with Multiple Word Burst Data Load operation disable the ECC functionality in S26KL-S/S26KS-S?

    No. Word programming with Multiple Word Burst Data Load operation will not disable the ECC functionality if it is not used more than once within a half-page without an erase.


    34. How long will it take for word programming with Multiple Word Burst Data Load to program a maximum of 256 words in S26KL-S/S26KS-S?

    The time taken for word programming with Multiple Word Burst Data Load to program a maximum of 256 words is the same as the Buffer Programming Time for one full page (256 words) ~475 µs.


    35. What happens if power loss occurs during erasing or programming?

    If power loss occurs during erasing or programming, the operation may be interrupted and data in the erasing or programming area may become unstable and cause data errors in flash memory.


    36. How do I recover the affected sector if a sudden power loss or flash RESET occurs during programming or erasing?

    If a sudden power loss or flash RESET occurs during programming or erasing, data in the target sector becomes unstable. To recover the affected sector, erase the target sectors again and rewrite the data. Sectors other than erasing or programming area will not be affected by a sudden power loss or flash RESET.

    See the Knowledge Base Article Recover Flash Devices when Power Failure or Reset Happens During a Program or Erase Operation - KBA218817.


    37. After programming to flash, will the data be lost if a power loss occurs during read?

    If a power loss happens during read, data will not be lost in the target sector.


    38. In what cases can ECC be invalid in FL-S/FL-L?

    ECC will be invalid in the following cases:

    • Multiple Page Program on the same ECC unit
    • Overwriting at the same address
    • Single Byte Programming

    Figure 5.  Valid and Invalid ECC Example

    39. How can ECC be re-enabled for an ECC unit that has been disabled?

    To re-enable ECC, the sector that includes the ECC unit must be erased.


    Figure 6.  Re-enabling ECC

    40. Where can I get the IBIS and Verilog models for flash devices?
    For IBIS and Verilog models, see

    41. Does an erase failure occur when the device reaches the erase limit? Is it necessary to retry the sector erase sequence after erase failure? Will erase failure happen in cases other than flash failure when the erase count limit is reached?
    Yes, erase failure might occur if the device reaches its erase limit. There is no need to retry the erase sequence. Flash operation will not fail except when there is a flash failure or when it reaches the erase count limit.


    42. Will the frequent erase failure on specific sectors affect nearby sectors?
    As erase is specific to sector and it will not affect other sectors.

    43. Will the maximum erase time increase if the power supply voltage, ambient temperature, and number of erase cycle increase?
    If the power supply voltage, ambient temperature, and number of erase cycle increase, processing time tends to increase but it will not exceed the maximum value mentioned in the datasheet. In addition, the data pattern before erasing also has an influence on the increase of the processing time.

    44. Consider that power is disconnected when the Sector Erase command is issued during partial erasure or during its waiting time (tSE). Is there a possibility that this situation might affect other sectors?
    When a Sector Erase command is executed, only the corresponding sector is affected. Other sectors are not affected.

    45. Can I issue a command immediately after issuing the WREN command or is it better to confirm that the WEL bit of the register has reached '1' (read the status register and confirm WEL = '1') before issuing the command?
    After issuing the WREN command, it is not necessary to read status register (RDSR)

    46. For flash devices with VIO option, can I connect both VCC and VIO to the same power supply?
    There will not be any problem if you want to tie VCC and VIO together with the same power supply of 3.3 V. The implementation fulfills the condition that 'during power-up or power-down VCC must always be greater than or equal to VIO (VCC ≥ VIO)’.

    47. The following external terminals of S25FL512S have built-in pull-up resistance.

    • # 1 HOLD#/IO3
    • # 3 RESET#/RFU_1
    • # 9 WP#/IO2
      What is the value and range of each internal pull-up resistance?

    For details on the pull-up resistors in S25FL512S, see Value of Internal Pull-Up Resistor on RESET#, HOLD#, and WP# for the S25FL-S and S25FL-L Series.

    48. Where can I find the BSDL file for boundary scan test of S29GL512S11TFB020?
    Since flash memories are not boundary scan devices, BSDL file cannot be provided.

    The connectivity between the host SoC/MCU and flash can be verified indirectly by accessing the flash memory from the host SoC/MCU.

    49. Which are the recommended sockets for flash devices?
    The following is the list of socket/adapters that support Cypress flash memory packages:

    • Meritec Inc.
    • Emulation Technology
    • Enplas-Tesco Inc.
    • Yamaichi Electronics USA Inc.

    For more information, contact the vendors. Cypress is not responsible for the product liability, service, and guarantee of any products manufactured and distributed by these vendors:

    50. Is it possible to write twice (erase write write to the same address) without reissuing the Erase command for the same address?
    It is physically possible to change 10, but if you write to the same Write Page twice, the built-in ECC function will be invalid. So, it is not recommended to write twice.

    51. Consider for example, a Suspend command (Interrupt command) is issued, for FL-S, during erase or write operation. Is it possible to read if flash is accessed again in the suspended state?
    If a Suspend command (Interrupt command) is issued during erase or write operation, reading is possible even if read access is provided by issuing a read command to flash again in the suspended state. However, if the voltage falls below VCC (low) = 2.3 V due to the instantaneous interruption, flash memory needs to be restarted.

    In the case of power interruption in the erase program, the data in the target area becomes undefined, so erasing and writing data are required. For details, see the section Power-Up and Power-Down in the device datasheet.

    52. Will there be an issue if I suspend an operation by software reset command and suspend command?
    When a writing or erasing operation is interrupted with the Software Reset command, the data in the target area becomes undefined.

    When writing or erasing operation is temporarily stopped by the Suspend command, there is no problem with the data. If you resume writing or erasing, the operation will complete normally.

    If the operation is suspended by a Power Down or Software Reset command without resuming, the write or erase operation will be interrupted and the data in the target area will be undefined.

    For sectors that became undefine, re-erasing and re-writing are required.

    53. What should I do when ErrorBit in the status register is set during Program/Erase?
    Execute Clear Status Register or Software Reset command.

    54. I am protecting a sector with Dynamic Protection Bit (DYB), but it seems like the sector can still be erased and written to.  What are the possible factors?”
    Check whether:

    • WREN is executed before executing DYB protect.
    • Power supply was restarted after DYB protect was executed.
    • Whether Software Reset is issued.

    55. When turning on the power supply with Power-on (Cold) Reset (POR), is it okay if the RESET # pin is fixed at High?
    According to the GL-T datasheet (11.3.1 Power-On (Cold) Reset (POR)), during the Cold Reset period all control signals including CE# and RESET# are ignored. RESET# may be High or Low during tVCS.

    56. I am considering replacing S29GL064N with S29GL064S, but the migration guide AN98586 excludes migration from 64 Mbit. Is it possible to replace S29GL064N with S29GL064S?
    It is possible to replace S29GL064N with S29GL064S. For details, see Migration from GL064N to GL064S.

    Here are some points that highlight the difference between 64 Mbit and 128 Mbit. For 128-Mbit device, data bus width is only x16 (WORD) mode. Also, there is no BYTE# pin for 128 Mbit and higher density devices. However, the status register of 128-Mbit device is the same as 64-Mbit device.

    In addition, 64 Mbit supports CFI v1.3, and 128 Mbit or higher density supports CFI v1.5. For other differences, see the device datasheet.


    57. Why is the ECC still enabled after writing the same page twice without erasing in S29GL-T device (erase write write to the same page)?

    ECC bits are also stored in flash non-volatile memory cells, so ECC bits can only be changed from ‘1’ to ‘0’. In the first write operation, ECC parity is calculated and written to the hidden ECC field. ECC is enabled automatically. For the second write operation, ECC parity will be re-calculated. If the new ECC parity requires any forbidden ‘0’ bit to ‘1’ bit transitions, the ECC function will be disabled. Otherwise, if ECC parity requires only ‘1’ bit to ‘0’ bit transitions, the ECC function will keep enabled.


    See the “Automatic ECC” section in AN200621.

    58. What is the minimum frequency of the serial flash?
    The minimum frequency is 1 Hz. The flash device can work between 1 Hz and the maximum frequency specified in the datasheet.


    59. What is the maximum X-ray dose for S26KS256S?

    For S26KS256S, it has been confirmed that X-ray exposure of 20Gy (2000Rad) is not a problem when the ECC function is enabled.


    For X-ray inspection recommendation, see AN98547 and AN98522.


    60. Is it possible to connect CK to PSC and CK# to PSC# for S26KL-S/S26KS-S device with DCARS enabled?

    When the DDR Center Aligned Read Strobe (DCARS) feature is enabled, a second differential Phase Shifted Clock input PSC/PSC# is used as the reference for the Read-Write Data Strobe (RWDS) edges instead of CK/CK#.


    It is possible to connect CK to PSC and CK# to PSC#. In this case, RWDS will behave like a non-DCARS part.