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DS42587 데이터시트(PDF) 23 Page - Advanced Micro Devices |
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DS42587 데이터시트(HTML) 23 Page - Advanced Micro Devices |
23 / 58 page DS42587 23 COMMAND DEFINITIONS Writing specific address and data commands or se- quences into the command register initiates device operations. Table 12 defines the valid register com- mand sequences. Writing incorrect address and data values or writing them in the improper se- quence resets the device to reading array data. All addresses are latched on the falling edge of WE# or CE#f, whichever happens later. All data is latched on the rising edge of WE# or CE#f, whichever hap- pens first. Refer to the AC Characteristics section for timing diagrams. Reading Array Data The device is automatically set to reading array data after device power-up. No commands are required to retrieve data. Each bank is ready to read array data after completing an Embedded Program or Embedded Erase algorithm. After the device accepts an Erase Suspend command, th e corresponding bank en te rs th e erase-sus- pend-read mode, after which the system can read data from any non-erase-suspended sector within the same bank. After completing a programming operation in the Erase Suspend mode, the system may once again read array data with the same exception. See the Erase Suspend/Erase Resume Commands sec- tion for more information. The system must issue the reset command to return a bank to the read (or erase-suspend-read) mode if DQ5 goes high during an active program or erase opera- tion, or if the bank is in the autoselect mode. See the next section, Reset Command, for more information. See also Requirements for Reading Array Data in the Device Bus Operations section for more information. The Flash Read-Only Operations table provides the read parameters, and Figure 14 shows the timing diagram. Reset Command Writing the reset command resets the banks to the read or erase-suspend-read mode. Address bits are don’t cares for this command. The reset command may be written between the se- quence cycles in an erase command sequence before erasing begins. This resets the bank to which the sys- tem was writing to reading array data. Once erasure begins, however, the device ignores reset commands until the operation is complete. The reset command may be written between the sequence cycles in a program command sequence before programming begins. This resets the bank to which the system was writing to reading array data. If the program command sequence is written to a bank that is in the Erase Suspend mode, writing the reset co mmand re turn s th at ban k to the era se- su s- pe nd- r e a d mo de. O n ce pr ogr a mming be gins, however, the device ignores reset commands until the operation is complete. The reset command may be written between the se- quence cycles in an autoselect command sequence. Once in the autoselect mode, the reset command must be written to return to reading array data. If a bank entered the autoselect mode while in the Erase Suspend mode, writing the reset command returns that bank to the erase-suspend-read mode. If DQ5 goes high during a program or erase operation, writing the reset command returns the banks to read- ing array data (or erase-suspend-read mode if that bank was in Erase Suspend). Autoselect Command Sequence The autoselect command sequence allows the host system to access the manufacturer and device codes, and determine whether or not a sector is protected. Table 12 shows the address and data requirements. The autoselect command sequence may be written to an address within a bank that is either in the read or erase-suspend-read mode. The autoselect command may not be written while the device is actively pro- gramming or erasing in the other bank. The autoselect command sequence is initiated by first writing two unlock cycles. This is followed by a third write cycle that contains the bank address and the au- to s e l e c t c o m m a n d . T h e ba nk th en e n t e r s th e autoselect mode. The system may read at any ad- dress within the same bank any number of times without initia ting an other autoselect comma nd sequence: s A read cycle at address (BA)XX00h (where BA is the bank address) returns the manufacturer code. s A read cycle at address (BA)XX01h in word mode (or (BA)XX02h in byte mode) returns the device code. s A read cycle to an address containing a sector ad- dress (SA) within the same bank, and the address 02h on A7–A0 in word mode (or the address 04h on A6–A-1 in byte mode) returns 01h if the sector is protected, or 00h if it is unprotected. (Refer to Ta- bles 5–6 for valid sector addresses). The system must write the reset command to return to reading array data (or erase-suspend-read mode if the bank was previously in Erase Suspend). |
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