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AT49F1614T Datasheet(PDF) 4 Page - ATMEL Corporation |
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AT49F1614T Datasheet(HTML) 4 Page - ATMEL Corporation |
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4 / 18 page  AT49F16X4(T) 4 the outputs of the device in a high impedance state. When a high level is reasserted on the RESET pin, the device returns to the Read or Standby mode, depending upon the state of the control inputs. By applying a 12V ± 0.5V input signal to the RESET pin any sector can be reprogrammed even if the sector lockout feature has been enabled (see Sector Programming Lockout Override section). ERASURE: Before a byte/word can be reprogrammed, it must be erased. The erased state of memory bits is a logi- cal “1”. The entire device can be erased by using the Chip Erase command or individual sectors can be erased by using the Sector Erase commands. CHIP ERASE: The entire device can be erased at one time by using the 6-byte chip erase software code. After the chip erase has been initiated, the device will internally time the erase operation so that no external clocks are required. The maximum time to erase the chip is t EC. If the sector lockout has been enabled, the Chip Erase will not erase the data in the sector that has been locked; it will erase only the unprotected sectors. After the chip erase, the device will return to the read or standby mode. SECTOR ERASE: As an alternative to a full chip erase, the device is organized into forty sectors (SA0 - SA39) that can be individually erased. The Sector Erase command is a six bus cycle operation. The sector address is latched on the falling WE edge of the sixth cycle while the 30H data input command is latched on the rising edge of WE. The sector erase starts after the rising edge of WE of the sixth cycle. The erase operation is internally controlled; it will automati- cally time to completion. The maximum time to erase a sec- tion is tSEC. When the sector programming lockout feature is not enabled, the sector will erase (from the same sector erase command). Once a sector has been protected, data in the protected sectors cannot be changed unless the RESET pin is taken to 12V ± 0.5V. An attempt to erase a sector that has been protected will result in the operation terminating in 2 µs. BYTE/WORD PROGRAMMING: Once a memory block is erased, it is programmed (to a logical “0”) on a byte-by-byte or on a word-by-word basis. Programming is accomplished via the internal device command register and is a 4-bus cycle operation. The device will automatically generate the required internal program pulses. Any commands written to the chip during the embedded programming cycle will be ignored. If a hardware reset hap- pens during programming, the data at the location being programmed will be corrupted. Please note that a data “0” cannot be programmed back to a “1”; only erase operations can convert “0”s to “1”s. Programming is completed after the specified t BP cycle time. The DATA polling feature or the toggle bit feature may be used to indicate the end of a pro- gram cycle. SECTOR PROGRAMMING LOCKOUT: Each sector has a programming lockout feature. This feature prevents pro- gramming of data in the designated sectors once the fea- ture has been enabled. These sectors can contain secure code that is used to bring up the system. Enabling the lock- out feature will allow the boot code to stay in the device while data in the rest of the device is updated. This feature does not have to be activated; any sector’s usage as a write protected region is optional to the user. Once the feature is enabled, the data in the protected sec- tors can no longer be erased or programmed when input levels of 5.5V or less are used. Data in the remaining sec- tors can still be changed through the regular programming method. To activate the lockout feature, a series of six pro- gram commands to specific addresses with specific data must be performed. Please refer to the Command Defini- tions table. SECTOR PROGRAMMING LOCKOUT OVERRIDE: The user can override the sector programming lockout by taking the RESET pin to 12V ± 0.5V. By doing this protected data can be altered through a chip erase, sector erase or byte/word programming. When the RESET pin is brought back to TTL levels the sector programming lockout feature is again active. ERASE SUSPEND/ERASE RESUME: The erase suspend command allows the system to interrupt a sector erase operation and then program or read data from a different sector within the same plane. Since this device has a dual plane architecture, there is no need to use the erase sus- pend feature while erasing a sector when you want to read data from a sector in the other plane. After the erase sus- pend command is given, the device requires a maximum time of 15 µs to suspend the erase operation. After the erase operation has been suspended, the plane which con- tains the suspended sector enters the erase-suspend-read mode. The system can then read data or program data to any other sector within the device. An address is not required during the erase suspend command. During a sector erase suspend, another sector cannot be erased. To resume the sector erase operation, the system must write the erase resume command. The erase resume command is a one bus cycle command, which does require the plane address (determined by A18 and A19). The device also supports an erase suspend during a complete chip erase. While the chip erase is suspended, the user can read from any sector within the memory that is protected. The com- mand sequence for a chip erase suspend and a sector erase suspend are the same. 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 pro- grammer to identify the correct programming algorithm for the Atmel product. |
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