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SST39LF100-45-4C-WI Datasheet(PDF) 2 Page - Silicon Storage Technology, Inc |
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SST39LF100-45-4C-WI Datasheet(HTML) 2 Page - Silicon Storage Technology, Inc |
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2 / 22 page  2 Data Sheet 1 Mbit Multi-Purpose Flash SST39LF100 / SST39VF100 ©2001 Silicon Storage Technology, Inc. S71129-02-000 6/01 363 Read The Read operation of the SST39LF/VF100 is controlled by CE# and OE#, both have to be low for the system to obtain data from the outputs. CE# is used for device selec- tion. When CE# is high, the chip is deselected and only standby power is consumed. OE# is the output control and is used to gate data from the output pins. The data bus is in high impedance state when either CE# or OE# is high. Refer to the Read cycle timing diagram for further details (Figure 2). Word-Program Operation The SST39LF/VF100 are programmed on a word-by-word basis. Before programming, one must ensure that the sec- tor in which the word is programmed is erased. The Pro- gram operation consists of three steps. The first step is the three-byte load sequence for Software Data Protection. The second step is to load word address and word data. During the Word-Program operation, the addresses are latched on the falling edge of either CE# or WE#, which- ever occurs last. The data is latched on the rising edge of either CE# or WE#, whichever occurs first. The third step is the internal Program operation which is initiated after the rising edge of the fourth WE# or CE#, whichever occurs first. The Program operation, once initiated, will be com- pleted within 20 µs. See Figures 3 and 4 for WE# and CE# controlled Program operation timing diagrams and Figure 13 for flowcharts. During the Program operation, the only valid reads are Data# Polling and Toggle Bit. During the internal Program operation, the host is free to perform addi- tional tasks. Any commands issued during the internal Pro- gram operation are ignored. Sector-Erase Operation The Sector-Erase operation allows the system to erase the device on a sector-by-sector basis. The sector architecture is based on uniform sector size of 2 KWord. The Sector- Erase operation is initiated by executing a six-byte com- mand sequence with Sector-Erase command (30H) and sector address (SA) in the last bus cycle. The address lines A11-A15 are used to determine the sector address. The sector address is latched on the falling edge of the sixth WE# pulse, while the command (30H) is latched on the ris- ing edge of the sixth WE# pulse. The internal Erase opera- tion begins after the sixth WE# pulse. The End-of-Erase operation can be determined using either Data# Polling or Toggle Bit methods. See Figure 8 for timing waveforms. Any commands issued during the Sector-Erase operation are ignored. Chip-Erase Operation The SST39LF/VF100 provide a Chip-Erase operation, which allows the user to erase the entire memory array to the “1” state. This is useful when the entire device must be quickly erased. The Chip-Erase operation is initiated by executing a six- byte command sequence with Chip-Erase command (10H) at address 5555H in the last byte sequence. The Erase operation begins with the rising edge of the sixth WE# or CE#, whichever occurs first. During the Erase operation, the only valid read is Toggle Bit or Data# Polling. See Table 4 for the command sequence, Figure 7 for timing diagram, and Figure 16 for the flowchart. Any commands issued dur- ing the Chip-Erase operation are ignored. Write Operation Status Detection The SST39LF/VF100 provide two software means to detect the completion of a Write (Program or Erase) cycle, in order to optimize the system write cycle time. The soft- ware detection includes two status bits: Data# Polling (DQ7) and Toggle Bit (DQ6). The End-of-Write detection mode is enabled after the rising edge of WE#, which ini- tiates the internal program or erase operation. The actual completion of the nonvolatile write is asynchro- nous with the system; therefore, either a Data# Polling or Toggle Bit read may be simultaneous with the completion of the write cycle. If this occurs, the system may possibly get an erroneous result, i.e., valid data may appear to con- flict with either DQ7 or DQ6. In order to prevent spurious rejection, if an erroneous result occurs, the software routine should include a loop to read the accessed location an additional two (2) times. If both reads are valid, then the device has completed the Write cycle, otherwise the rejec- tion is valid. Data# Polling (DQ7) When the SST39LF/VF100 are in the internal Program operation, any attempt to read DQ7 will produce the com- plement of the true data. Once the Program operation is completed, DQ7 will produce true data. The device is then ready for the next operation. During internal Erase opera- tion, any attempt to read DQ7 will produce a ‘0’. Once the internal Erase operation is completed, DQ7 will produce a ‘1’. The Data# Polling is valid after the rising edge of fourth WE# (or CE#) pulse for Program operation. For Sector- or Chip-Erase, the Data# Polling is valid after the rising edge of sixth WE# (or CE#) pulse. See Figure 5 for Data# Polling timing diagram and Figure 14 for a flowchart. |
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