CFI Query Command Interface Sample Clauses

CFI Query Command Interface. The CFI Query structure is accessed similar to the existing “ID Mode” or “JEDEC ID” access for nonvolatile memories, but uses a different, non-conflicting command code. The Query access command is 98h, while the JEDEC ID mode access mode is 90h. The Query addressing is always relative to the device word (largest supported) with data always presented on the lowest order byte (D7 - D0 outputs). Nonvolatile memory devices are assumed to power up in a read-only state. Independent of that assumption, the Query structure contents must be able to be read at the specific address locations following a single system write cycle where: 1) a 98h Query command code is written to 55h address location within the device’s address space (in maximum device bus-width), and 2) the device is in any valid read state, such as “Read Array” or “Read ID Data.” Other device states may exist within a long sequence of commands or data input; such sequences must first be completed or terminated before the writing of the 98h Query command code will result in valid Query data structure output. Note that for devices wider than 8 bits, the valid Query access code has all zeroes (0’s) in upper bytes of the data bus. Thus the 16-bit Query command code is 0098h and the 32- bit Query command code is 00000098h. A CFI-compliant device must allow selection and de-selection of the Query output mode to and from normal read array operation with a single command write cycle so that the desired data are accessible in the second of two active bus cycles, i.e. bus cycles in which the devices Chip Enable(s) are active. Table 3.1 Command Write Cycles for Query Select & Deselect Command # of Cycles First Bus Cycle Second Bus Cycle