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AM42DL640AG70IT 데이터시트(PDF) 13 Page - SPANSION |
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AM42DL640AG70IT 데이터시트(HTML) 13 Page - SPANSION |
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13 / 62 page  12 Am42DL640AG October 22, 2002 PR E L I M I N A R Y pins DQ14–DQ8 are tri-stated, and the DQ15 pin is used as an input for the LSB (A-1) address function. Requirements for Reading Array Data To read array data from the outputs, the system must drive the CE#f and OE# pins to V IL. CE#f is the power control and selects the device. OE# is the output con- trol and gates array data to the output pins. WE# should remain at V IH . T h e C IOf p i n d e te r m i n e s whether the device outputs array data in words or bytes. The internal state machine is set for reading array data upon device power-up, or after a hardware reset. This ensures that no spurious alteration of the memory content occurs during the power transition. No com- mand is necessary in this mode to obtain array data. Standard microprocessor read cycles that assert valid addresses on the device address inputs produce valid data on the device data outputs. Each bank remains enabled for read access until the command register contents are altered. Refer to the AC Flash Read-Only Operations table for timing specifications and to Figure 15 for the timing di- agram. I CC1 in the DC Characteristics table represents the active current specification for reading array data. Writing Commands/Command Sequences To write a command or command sequence (which in- cludes programming data to the device and erasing sectors of memory), the system must drive WE# and CE#f to V IL, and OE# to VIH. For program operations, the CIOf pin determines whether the device accepts program data in bytes or words. Refer to “Word/Byte Configuration” for more in- formation. The device features an Unlock Bypass mode to facil- itate faster programming. Once a bank enters the Un- lock Bypass mode, only two write cycles are required to program a word or byte, instead of four. The “Byte/Word Program Command Sequence” section has details on programming data to the device using both standard and Unlock Bypass command se- quences. An erase operation can erase one sector, multiple sec- tors, or the entire device. Table 3 indicates the address space that each sector occupies. Similarly, a “sector address” is the address bits required to uniquely select a sector. The “Command Definitions” section has de- tails on erasing a sector or the entire chip, or suspend- ing/resuming the erase operation. The device address space is divided into four banks. A “bank address” is the address bits required to uniquely select a bank. I CC2 in the DC Characteristics table represents the ac- tive current specification for the write mode. The AC Characteristics section contains timing specification tables and timing diagrams for write operations. Accelerated Program Operation The device offers accelerated program operations through the ACC function. This is one of two functions provided by the WP#/ACC pin. This function is prima- rily intended to allow faster manufacturing throughput at the factory. If the system asserts V HH on this pin, the device auto- matically enters the aforementioned Unlock Bypass mode, temporarily unprotects any protected sectors, and uses the higher voltage on the pin to reduce the time required for program operations. The system would use a two-cycle program command sequence as required by the Unlock Bypass mode. Removing V HH from the WP#/ACC pin returns the device to nor- mal operation. Note that V HH must not be asserted on WP#/ACC for operations other than accelerated pro- gramming, or device damage may result. In addition, the WP#/ACC pin must not be left floating or uncon- nected; inconsistent behavior of the device may result. See “Write Protect (WP#)” on page 18 for related in- formation. Autoselect Functions If the system writes the autoselect command se- quence, the device enters the autoselect mode. The system can then read autoselect codes from the inter- nal register (which is separate from the memory array) on DQ15–DQ0. Standard read cycle timings apply in this mode. Refer to the Sector/Sector Block Protection and Unprotection and Autoselect Command Se- quence sections for more information. Simultaneous Read/Write Operations with Zero Latency This device is capable of reading data from one bank of memory while programming or erasing in the other bank of memory. An erase operation may also be sus- pended to read from or program to another location within the same bank (except the sector being erased). Figure 22 shows how read and write cycles may be initiated for simultaneous operation with zero latency. I CC6f and ICC7f in the table represent the cur- rent specifications for read-while-program and read-while-erase, respectively. Standby Mode When the system is not reading or writing to the de- vice, it can place the device in the standby mode. In this mode, current consumption is greatly reduced, and the outputs are placed in the high impedance state, independent of the OE# input. |
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