NOR Flash FAQs - KBA222273

Version: *D


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.

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.

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.

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.

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.

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).

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.

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 ()

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.

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.

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.

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.

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.

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 details of differences between them.

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.

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 


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.

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.

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.

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

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.

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.


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.

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.

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.


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.

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.

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

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.


Is it okay to connect the RFU pin to VDD or GND?


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


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 as long as the sector is blank or erased, but it is not efficient. This is because it 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.


How does Word Programming with Multiple Word Burst Data Load operation works 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.


Will Word Programming with Multiple Word Burst Data Load operation disable the ECC functionality in S26KL-S/S26KS-S?


No. It will not disable the ECC functionality if not used more than once within a half-page without an erase.


How long will it take to complete Word Programming with Multiple Word Burst Data Load to program max 256 words in S26KL-S/S26KS-S?


It will take same amount of time as Buffer Programming Time for one full page (256 words) ~475 µs


What happens if power loss occurs during erasing or programming?


If power loss happens 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.


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


If a sudden power loss or flash RESET happens 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


After programming to flash, if power loss happens during read, will the data lost?


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


What are the cases where the ECC can be invalid in FL-S/FL-L?


In the following cases, ECC will become invalid:

Multiple Page Program on the same ECC unit

Overwriting at the same address

Single Byte Programming


Figure 5. Valid and Invalid ECC example

How to re-enable ECC for an ECC unit that has been disabled?


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


Figure 6. How to re-enable ECC

Where can I get the IBIS and Verilog models for flash devices?

For IBIS and Verilog models, see



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.

Will the frequent erase failure on specific sectors affect nearby sectors?

As erase is specific to sector and it will affect other sectors.

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.

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.

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)

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)’.