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AM49DL640AG70IS 데이터시트(PDF) 28 Page - Advanced Micro Devices |
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AM49DL640AG70IS 데이터시트(HTML) 28 Page - Advanced Micro Devices |
28 / 65 page April 1, 2003 Am49DL640AG 27 PR E L I M I N A R Y Sector command sequence. The device continues to access the SecSi Sector region until the system is- sues the four-cycle Exit SecSi Sector command se- quence. The Exit SecSi Sector command sequence returns the device to normal operation. The SecSi Sector is not accessible when the device is executing an Embedded Program or embedded Erase algorithm. Table 12 shows the address and data requirements for both command sequences. See also “SecSi™ (Se- cured Silicon) Sector Flash Memory Region” for further information. Note that the ACC function and unlock by- pass modes are not available when the SecSi Sector is enabled. Byte/Word Program Command Sequence The system may program the device by word or byte, depending on the state of the CIOf pin. Programming is a four-bus-cycle operation. The program command sequence is initiated by writing two unlock write cy- cles, followed by the program set-up command. The program address and data are written next, which in turn initiate the Embedded Program algorithm. The system is not required to provide further controls or timings. The device automatically provides internally generated program pulses and verifies the pro- grammed cell margin. Table 12 shows the address and data requirements for the byte program command sequence. When the Embedded Program algorithm is complete, that bank then returns to the read mode and ad- dresses are no longer latched. The system can deter- mine the status of the program operation by using DQ7, DQ6, or RY/BY#. Refer to the Flash Write Oper- ation Status section for information on these status bits. Any commands written to the device during the Em- bedded Program Algorithm are ignored. Note that a hardware reset immediately terminates the program operation. The program command sequence should be reinitiated once that bank has returned to the read mode, to ensure data integrity. Note that the SecSi Sector, autoselect, and CFI functions are unavailable when a program operation is in progress Programming is allowed in any sequence and across sector boundaries. A bit cannot be programmed from “0” back to a “1.” Attempting to do so may cause that bank to set DQ5 = 1, or cause the DQ7 and DQ6 status bits to indicate the operation was success- ful. However, a succeeding read will show that the data is still “0.” Only erase operations can convert a “0” to a “1.” Unlock Bypass Command Sequence The unlock bypass feature allows the system to pro- gram bytes or words to a bank faster than using the standard program command sequence. The unlock bypass command sequence is initiated by first writing two unlock cycles. This is followed by a third write cycle containing the unlock bypass command, 20h. That bank then enters the unlock bypass mode. A two-cycle unlock bypass program command sequence is all that is required to program in this mode. The first cycle in this sequence contains the unlock bypass pro- gram command, A0h; the second cycle contains the program address and data. Additional data is pro- grammed in the same manner. This mode dispenses with the initial two unlock cycles required in the stan- dard program command sequence, resulting in faster total programming time. Table 12 shows the require- ments for the command sequence. During the unlock bypass mode, only the Unlock By- pass Program and Unlock Bypass Reset commands are valid. To exit the unlock bypass mode, the system must issue the two-cycle unlock bypass reset com- mand sequence. The first cycle must contain the bank address and the data 90h. The second cycle need only contain the data 00h. The bank then returns to the read mode. The device offers accelerated program operations through the WP#/ACC pin. When the system asserts V HH on the WP#/ACC pin, the device automatically en- ters the Unlock Bypass mode. The system may then write the two-cycle Unlock Bypass program command sequence. The device uses the higher voltage on the WP#/ACC pin to accelerate the operation. Note that the WP#/ACC pin must not be at V HH any operation other than accelerated programming, or device dam- age may result. In addition, the WP#/ACC pin must not be left floating or unconnected; inconsistent behavior of the device may result. Figure 4 illustrates the algorithm for the program oper- ation. Refer to the Erase and Program Operations table in the AC Characteristics section for parameters, and Figure 19 for timing diagrams. |
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