Flash chip is a widely used storage device. In order to save PCB area and reduce chip startup pins, SPI serial Flash using SPI communication method has become the mainstream application. The smart door lock circuit designed by the author is divided into front panel main control circuit The front panel consists of the main control module, touch buttons, fingerprint identification and card swiping modules; the rear panel includes the slave MCU, external FLASH, battery circuit, motor drive control circuit and configuration buttons.

The internal Flash capacity of the smart door lock slave MCU SMT8L151K4T6 is only 16 Kbytes, and an external Flash is required to store security data, configuration information, etc. We choose Zhaoyi Innovation GD25Q32CSIG as the external flash, with a capacity of 32M-bit, which can meet the design needs.

GD25Q32CSIG main features:

1. Capacity 32M-bit.

2. Support standard SPI, Dual SPI, Quad SPI.

3. High clock frequency support, the fast read rate is 80MHz under 30PF load, the data transmission rate of dual output can reach 240Mbits/s, and the data transmission rate of quad output can reach 480Mbits/s.

4. Support software/hardware write protection.

5. Minimum 100,000 program/erase cycles.

6. The data storage time is up to 20 years.

7. The typical value of standby current is 0.1uA, and the typical value of deep power saving state current is 0.1uA.

8. It has 3*1024 bytes of security registers with OTP lock.

9. Power supply voltage: 2.7V-3.6V.

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