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AM29PDLI27H 数据表(PDF) 13 Page - SPANSION |
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AM29PDLI27H 数据表(HTML) 13 Page - SPANSION |
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13 / 68 page ![]() June 30, 2003 Am29PDL127H 11 ADV ANCE I N FO RMAT I O N DEVICE BUS OPERATIONS This section describes the requirements and use of the device bus operations, which are initiated through the internal command register. The command register itself does not occupy any addressable memory loca- tion. The register is a latch used to store the com- mands, along with the address and data information needed to execute the command. The contents of the register serve as inputs to the internal state machine. The state machine outputs dictate the function of the device. Table 1 lists the device bus operations, the in- puts and control levels they require, and the resulting output. The following subsections describe each of these operations in further detail. Table 1. Am29PDL127H Device Bus Operations Legend: L = Logic Low = V IL, H = Logic High = VIH, VID = 11.5–12.5 V, VHH = 8.5–9.5 V, X = Don’t Care, SA = Sector Address, A IN = Address In, DIN = Data In, DOUT = Data Out Notes: 1. The sector protect and sector unprotect functions may also be implemented via programming equipment. See the High Voltage Sector Protection section. 2. WP#/ACC must be high when writing to sectors 0, 1, 268, or 269. Requirements for Reading Array Data To read array data from the outputs, the system must drive the OE# and appropriate CE# pins to V IL. CE# is the power control. OE# is the output control and gates array data to the output pins. WE# should remain at V IH. 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 Characteristics table for timing specifi- cations and to Figure 11 for the timing diagram. I CC1 in the DC Characteristics table represents the active cur- rent specification for reading array data. Random Read (Non-Page Read) Address access time (t ACC) is equal to the delay from stable addresses to valid output data. The chip enable access time (t CE ) is the delay from the stable ad- dresses and stable CE# to valid data at the output in- puts. The output enable access time is the delay from the falling edge of the OE# to valid data at the output inputs (assuming the addresses have been stable for at least t ACC–tOE time). Page Mode Read The device is capable of fast page mode read and is compatible with the page mode Mask ROM read oper- ation. This mode provides faster read access speed for random locations within a page. Address bits A22–A3 select an 8 word page, and address bits A2–A0 select a specific word within that page. This is an asynchronous operation with the microprocessor supplying the specific word location. The random or initial page access is t ACC or tCE and subsequent page read accesses (as long as the loca- tions specified by the microprocessor falls within that page) is equivalent to t PACC. When CE# is deasserted (CE#=V IH), the reassertion of CE# for subsequent ac- Operation CE# OE# WE# RESET# WP#/ACC Addresses (A22–A0) DQ15– DQ0 Read L L H H X A IN D OUT Write L H L H X AIN DIN Standby V IO± 0.3 V XX V IO ± 0.3 V X (Note 2) X High-Z Output Disable L H H H X X High-Z Reset X X X L X X High-Z Temporary Sector Unprotect (High Voltage) XX X VID XAIN DIN |
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