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.
Table 22. Query Structure Overview(1)
20h CFI Query Identification String
Command set ID and algorithm data offset
36h System Interface Information
Device timing & voltage information
4Eh Device Geometry Definition
Flash device layout
Primary Algorithm-specific extended
Additional information specific to the Primary
C2h Security code area
64 bit unique device number
1. Query data are always presented on the lowest order data outputs.
Table 23. CFI Query Identification String(1)
10h 20h 0051h
11h 22h 0052h Query unique ASCII string "QRY"
12h 24h 0059h
26h 0002h Primary Algorithm Command Set and Control Interface ID code 16 bit
28h 0000h ID code defining a specific algorithm
15h 2Ah 0040h
Address for Primary Algorithm extended query table (see Table 26)
16h 2Ch 0000h
P = 40h
2Eh 0000h Alternate Vendor Command Set and Control Interface ID code second
30h 0000h vendor - specified algorithm supported
19h 32h 0000h
Address for Alternate Algorithm extended Query table
1Ah 34h 0000h
1. Query data are always presented on the lowest order data outputs (DQ7-DQ0) only. DQ8-DQ15 are ‘0’.