W25Q256FVFIG

The W25Q256FVFIG is a 256-Mbit (32-MByte) serial NOR Flash memory from Winbond’s SpiFlash family, housed in a 16-pin SOIC-300 package with an additional /RESET pin. It provides high-density non-volatile storage for code shadowing, execute-in-place (XIP), and data logging applications.

The device supports four SPI modes: standard SPI (1-bit serial), Dual Output SPI, Dual I/O SPI, and Quad I/O SPI. At 104 MHz clock, Quad I/O achieves an effective 416 MHz data rate (50 MB/s), outperforming many parallel Flash memories while using only 6 pins. The QPI (Quad Peripheral Interface) mode enables all four data pins for both command and address phases, reducing instruction overhead to just 8 clock cycles for true XIP operation.

The 256-Mbit density requires 3-byte or 4-byte addressing. The device supports both modes for backward compatibility (3-byte) and full address space access (4-byte). The 16-pin SOIC package provides a dedicated /RESET pin (pin 9) that is not available on 8-pin packages, enabling hardware reset without SPI commands.

Memory organization includes 131,072 programmable pages of 256 bytes, 8,192 erasable 4-KB sectors, and 512 erasable 64-KB blocks. The 4-KB sector size supports fine-grained data management. Erase/program suspend and resume allows interrupting a long erase operation to read or program a different area, reducing system latency.

Security features include software/hardware write protection, power-supply lock-down, individual sector/block protection, three 256-byte security registers with OTP locks, a 64-bit unique serial number, and an SFDP (Serial Flash Discoverable Parameters) register for auto-detection.

The W25Q256FVFIG is part of the FV generation which is now discontinued. Winbond recommends migrating to the W25Q256JV series (JVFIQ or JVFIM suffixes), which offers the same functionality with improved performance and continued production support.

**SPI Interface:** The W25Q256FV uses a standard SPI interface with /CS (chip select), CLK (serial clock), DI/IO0 (data in), DO/IO1 (data out), /WP/IO2, and /HOLD/IO3 pins. In standard SPI mode, DI carries command/address/data and DO returns data. In Quad SPI mode, all four I/O pins carry address and data in parallel, quadrupling throughput. QPI mode extends quad operation to the command phase as well.

**3/4-Byte Addressing:** The 256-Mbit density exceeds the 128-Mbit boundary of 24-bit (3-byte) addressing. The device defaults to 3-byte addressing for compatibility and can switch to 4-byte addressing via the Enter 4-Byte Address Mode instruction. In 3-byte mode, only the lower 128 Mbit is accessible. In 4-byte mode, all 256 Mbit is accessible with a 32-bit address.

**Page Program and Erase:** Programming loads up to 256 bytes into an internal buffer, then writes the entire page in approximately 3 ms (typical). Sectors (4 KB) erase in approximately 400 ms, blocks (32/64 KB) in 800 ms/2 s, and the entire chip in approximately 200 s. The suspend/resume feature allows reading from non-suspended areas during long erase operations.

**Status and Protection:** Two status registers (SR1, SR2) control write protection, quad enable, and address mode. Block protect bits in SR1 define protected address ranges. The SR2 Quad Enable bit must be set before using Quad SPI instructions. Write protection can be enhanced with the /WP pin (active low) which locks the status register when asserted.