Common flash interface (CFI)
Appendix B Common flash interface (CFI)
The common flash interface is a JEDEC approved, standardized data structure that can be
read from the flash memory device. It allows a system software to query the device to
determine various electrical and timing parameters, density information and functions
supported by the memory. The system can interface easily with the device, enabling the
software to upgrade itself when necessary.
When the CFI Query command is issued the device enters CFI query mode and the data
structure is read from the memory. Table 22, Table 23, Table 24, Table 25, Table 26 and
Table 27 show the addresses used to retrieve the data.
The CFI data structure also contains a security area where a 64-bit unique security number
is written (see Table 27: Security code area). This area can be accessed only in read mode
by the final user. It is impossible to change the security number after it has been written by
Numonyx. Issue a Read command to return to read mode.
Table 22. Query structure overview (1)
x 16 x 8
10h 20h CFI query identification string
Command set ID and algorithm data offset
1Bh 36h System interface information
Device timing & voltage information
27h 4Eh Device geometry definition
Flash device layout
Primary algorithm-specific extended
Additional information specific to the
primary algorithm (optional)
61h C2h Security code area
64-bit unique device number
1. Query data are always presented on the lowest order data outputs.