NOR Flash FAQs - KBA222273

Version: **


Does the sector or chip erase time increase by 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 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 does some Cypress datasheet 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 as it is more efficient.  However, it is recommended to load the buffer with the maximum number of words, as 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 Byte pin open?

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

 
How can I connect byte access (how can I connect 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 A-1 pin to the lowest address A0 of the CPU. DQ14-8 will be tri-stated (high-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:
·θja 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 (℃)

It is stated in the datasheet that data retention of Flash 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 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 factors 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.

In the datasheet, it is shown 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 the same density S25FL128S?

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 recommended that you strongly consider S25FL128S.