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AT29BV040A Datasheet(PDF) 3 Page - ATMEL Corporation |
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AT29BV040A Datasheet(HTML) 3 Page - ATMEL Corporation |
3 / 14 page 3 AT29BV040A 0383G–FLASH–5/03 Any attempt to write to the device without the 3-byte command sequence will start the internal write timers. No data will be written to the device; however, for the duration of t WC, a read operation will effectively be a polling operation. After the software data protection’s 3-byte command code is given, a byte load is per- formed by applying a low pulse on the WE or CE input with CE or WE low (respectively) and OE high. The address is latched on the falling edge of CE or WE, whichever occurs last. The data is latched by the first rising edge of CE or WE. The 256 bytes of data must be loaded into each sector. Any byte that is not loaded dur- ing the programming of its sector will be indeterminate. Once the bytes of a sector are loaded into the device, they are simultaneously programmed during the internal pro- gramming period. After the first data byte has been loaded into the device, successive bytes are entered in the same manner. Each new byte to be programmed must have its high-to-low transition on WE (or CE) within 150 µs of the low-to-high transition of WE (or CE) of the preceding byte. If a high-to-low transition is not detected within 150 µs of the last low-to-high transition, the load period will end and the internal programming period will start. A8 to A18 specify the sector address. The sector address must be valid during each high-to-low transition of WE (or CE). A0 to A7 specify the byte address within the sector. The bytes may be loaded in any order; sequential loading is not required. HARDWARE DATA PROTECTION: Hardware features protect against inadvertent programs to the AT29BV040A in the following ways: (a) VCC sense – if VCC is below 1.8V (typical), the program function is inhibited; (b) VCC power on delay – once VCC has reached the VCC sense level, the device will automatically time out 10 ms (typical) before programming; (c) Program inhibit – holding any one of OE low, CE high or WE high inhibits program cycles; and (d) Noise filter – pulses of less than 15 ns (typical) on the WE or CE inputs will not initiate a program cycle. INPUT LEVELS: While operating with a 2.7V to 3.6V power supply, the address inputs and control inputs (OE, CE and WE) may be driven from 0 to 5.5V without adversely affecting the operation of the device. The I/O lines can only be driven from 0 to VCC + 0.6V. PRODUCT IDENTIFICATION: The product identification mode identifies the device and manufacturer as Atmel. It may be accessed by hardware or software operation. The hardware operation mode can be used by an external programmer to identify the correct programming algorithm for the Atmel product. In addition, users may wish to use the software product identification mode to identify the part (i.e. using the device code), and have the system software use the appropriate sector size for program operations. In this manner, the user can have a common board design for 256K to 4-megabit densities and, with each density’s sector size in a memory map, have the system software apply the appropriate sector size. For details, see Operating Modes (for hardware operation) or Software Product Identifi- cation. The manufacturer and device code is the same for both modes. DATA POLLING: The AT29BV040A features DATA polling to indicate the end of a program cycle. During a program cycle an attempted read of the last byte loaded will result in the complement of the loaded data on I/O7. Once the program cycle has been completed, true data is valid on all outputs and the next cycle may begin. DATA polling may begin at any time during the program cycle. TOGGLE BIT: In addition to DATA polling the AT29BV040A provides another method for determining the end of a program or erase cycle. During a program or erase opera- tion, successive attempts to read data from the device will result in I/O6 toggling between one and zero. Once the program cycle has completed, I/O6 will stop toggling |
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