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M29F040B Datasheet(PDF) 4 Page - STMicroelectronics |
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M29F040B Datasheet(HTML) 4 Page - STMicroelectronics |
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4 / 20 page  M29F040B 4/20 SIGNAL DESCRIPTIONS See Figure 1, Logic Diagram, and Table 1, Signal Names, for a brief overview of the signals connect- ed to this device. Address Inputs (A0-A18). The Address Inputs select the cells in the memory array to access dur- ing Bus Read operations. During Bus Write opera- tions they control the commands sent to the Command Interface of the internal state machine. Data Inputs/Outputs (DQ0-DQ7). The Data In- puts/Outputs output the data stored at the selected address during a Bus Read operation. During Bus Write operations they represent the commands sent to the Command Interface of the internal state machine. Chip Enable (E). The Chip Enable, E, activates the memory, allowing Bus Read and Bus Write op- erations to be performed. When Chip Enable is High, VIH, all other pins are ignored. Output Enable (G). The Output Enable, G, con- trols the Bus Read operation of the memory. Write Enable (W). The Write Enable, W, controls the Bus Write operation of the memory’s Com- mand Interface. VCC Supply Voltage. The VCC Supply Voltage supplies the power for all operations (Read, Pro- gram, Erase etc.). The Command Interface is disabled when the VCC Supply Voltage is less than the Lockout Voltage, VLKO. This prevents Bus Write operations from ac- cidentally damaging the data during power up, power down and power surges. If the Program/ Erase Controller is programming or erasing during this time then the operation aborts and the memo- ry contents being altered will be invalid. A 0.1µF capacitor should be connected between the VCC Supply Voltage pin and the VSS Ground pin to decouple the current surges from the power supply. The PCB track widths must be sufficient to carry the currents required during program and erase operations, ICC4. VSS Ground. The VSS Ground is the reference for all voltage measurements. BUS OPERATIONS There are five standard bus operations that control the device. These are Bus Read, Bus Write, Out- put Disable, Standby and Automatic Standby. See Table 4, Bus Operations, for a summary. Typically glitches of less than 5ns on Chip Enable or Write Enable are ignored by the memory and do not af- fect bus operations. Bus Read. Bus Read operations read from the memory cells, or specific registers in the Com- mand Interface. A valid Bus Read operation in- volves setting the desired address on the Address Inputs, applying a Low signal, VIL, to Chip Enable and Output Enable and keeping Write Enable High, VIH. The Data Inputs/Outputs will output the value, see Figure 8, Read Mode AC Waveforms, and Table 11, Read AC Characteristics, for details of when the output becomes valid. Bus Write. Bus Write operations write to the Command Interface. A valid Bus Write operation begins by setting the desired address on the Ad- dress Inputs. The Address Inputs are latched by the Command Interface on the falling edge of Chip Enable or Write Enable, whichever occurs last. The Data Inputs/Outputs are latched by the Com- mand Interface on the rising edge of Chip Enable or Write Enable, whichever occurs first. Output En- able must remain High, VIH, during the whole Bus Write operation. See Figures 9 and 10, Write AC Waveforms, and Tables 12 and 13, Write AC Characteristics, for details of the timing require- ments. Output Disable. The Data Inputs/Outputs are in the high impedance state when Output Enable is High, VIH. Standby. When Chip Enable is High, VIH, the Data Inputs/Outputs pins are placed in the high- impedance state and the Supply Current is re- duced to the Standby level. When Chip Enable is at VIH the Supply Current is reduced to the TTL Standby Supply Current, ICC2. To further reduce the Supply Current to the CMOS Standby Supply Current, ICC3, Chip Enable should be held within VCC ± 0.2V. For Standby current levels see Table 10, DC Characteristics. During program or erase operations the memory will continue to use the Program/Erase Supply Current, ICC4, for Program or Erase operations un- til the operation completes. |
Similar Part No. - M29F040B_05 |
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Similar Description - M29F040B_05 |
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