S28HL-T/S28HS-T SEMPER™ NOR flash: Switching the mode between Octal and legacy SPI - KBA233741

[Chelladurai]

Version: **

S28HL-T and S28HS-T series SEMPER™ NOR flash with Octal interface can support legacy SPI (x1) mode and Octal (x8) mode, with legacy SPI as the default. The two modes can be switched from one to the other as necessary. It requires some configurations and special notices on both the host controller and the flash device.

Switch from legacy SPI (x1) mode to Octal (x8) SDR mode:

1. The host controller in legacy SPI (x1) mode communicates with the flash through the legacy SPI (1S-1S-1S) protocol to access and set CFR5V/N[1:0] = 01b.
2. The host controller switches the work mode from legacy SPI to Octal (8S-8S-8S). The host controller is now in Octal (x8) SDR mode.
3. Now, the host controller can communicate with the flash in Octal (8S-8S-8S) protocol. Depending on whether the register write was to the volatile or non-volatile register, the following will happen:
   1. If CFR5V[1:0] = 01b, the flash will revert to legacy SPI mode after POR/reset.
   2. If CFR5N [1:0] = 01b, the flash will keep Octal SDR mode for further boots.

Switch from legacy SPI (x1) mode to Octal (x8) DDR mode:

1. The host controller in legacy SPI (x1) mode communicates with the flash through the legacy SPI (1S-1S-1S) protocol to access and set CFR5V/N[1:0] = 11b.
2. The host controller switches the work mode from legacy SPI to Octal (8D-8D-8D). The host controller is now in Octal (x8) DDR mode.
3. Now, the host controller can communicate with the flash in Octal (8D-8D-8D) protocol. Depending on whether the register write was to the volatile or non-volatile register, the following will happen:
   1. If CFR5V[1:0] = 11b, the flash will revert to legacy SPI mode after POR/reset.
   2. If CFR5N [1:0] = 11b, the flash will keep Octal DDR mode for further boots.

Switch from Octal (x8) mode to legacy SPI (x1) mode:

1. The host controller in Octal (x8) mode communicates with the flash through the Octal (8S-8S-8S or 8D-8D-8D) protocol to access and set CFR5V/N[1:0] = 00b.
2. The host controller switches the work mode from Octal (x8) to legacy SPI. The host controller is now in legacy SPI (x1) mode.
3. Now, the host controller can communicate with the flash in legacy SPI (1S-1S-1S) protocol. To set the chip in legacy SPI mode by default, access and set the non-volatile version register CFR5N[1:0] = 00b.