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Sectors are the erase units of a flash memory. Infineon serial NOR flash devices offer a flexible sector architecture with two options:
- Uniform sector: The entire flash array is divided into equally sized uniform sectors
- Hybrid sector size: Physical set of 4-KB sectors present at the top or bottom of the address space
Whether a device supports hybrid sector architecture or not can be determined through the model number in the ordering part number (OPN) of the device or the configuration register settings. See the respective device datasheet for detailed OPN definition including model number information.
Configuration register settings can be modified to change the default sector architecture. For example, in the FS-S device family, one particular bit of the configuration register (CR3NV [3]) enables or disables the 4-KB parameter sectors. The default state of CR3NV[3] bit is 0, which means 4-KB sectors are enabled. The configuration register can be programmed to set the CR3NV[3] bit to 1 to disable 4-KB parameter sector overlay and choose the uniform sector size option. The CR3NV[3] bit is an OTP (one time programmable) bit, which means it can be programmed only once in the entire lifecycle of the flash memory.
4-KB parameter sectors can be at the bottom or top of the flash device. Their location can be changed by modifying the TBPARM bit of the configuration register. TBPARM is also an OTP bit. For example, the default value of the TBPARM bit is 0, indicating that the 4-KB physical sectors are located at the bottom (low address). Programming the configuration register to set TBPARM bit to ‘1’ will change the location of the parameter sectors to top (high address) space.
There are special commands to perform sector erase operation on these 4-KB parameter sectors. The P4E (20h) and the 4P4E (21h) commands can be used to erase parameter sectors. The P4E command can take 3-byte as well as 4-bytes address, whereas the 4P4E command always expects 4-bytes address. The P4E and 4P4E commands are ignored when the device is configured for uniform sector size option.
Examples:
Sector organization in FL-S and FS-S devices –
- S25FL128S/S25FL256S
- Uniform sector: The entire flash is divided into uniform 256-KB sectors
- Hybrid sector size: Physical set of thirty-two 4-KB sectors present at the top or bottom of the address space; all remaining sectors of 64-KB size.
- S25FS512S
- Uniform sector: The entire flash is divided into uniform 256-KB sectors
- Hybrid sector size: Physical set of eight 4-KB sectors and one 224-KB sector present at the top or bottom of the address space; all remaining sectors are of 256-KB size.
In FL-S device, the 64-KB sector erase command (D8h or DCh) can also be used to erase a group of sixteen 4-KB parameter sectors. The advanced sector protection feature provides a PPB and a DYB protection bit for each of these thirty-two 4-KB parameter sectors. If the 64-KB sector erase command is applied to a certain 64-KB range such that it includes a protected 4-KB sector, the erase operation will not be executed on the protected range of memory and the E_ERR bit in the status register will be set.
On the other hand, in the FS-S family, only the parameter sector erase commands (20h or 21h) must be used to erase 4-KB sectors individually. The uniform sector erase command (D8h or DCh) should be used to erase all remaining sectors (224-KB sector and 256-KB sectors). The same conditions are applicable for 128Mb/256Mb FS-S device parameter sector and uniform sectors (32-KB sector and 64-KB sectors) as well.
