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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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FM24W256-GTR датащи(PDF) 4 Page - Ramtron International Corporation |
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FM24W256-GTR датащи(HTML) 4 Page - Ramtron International Corporation |
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4 / 13 page  FM24W256 - 256Kb Wide Voltage I2C F-RAM Rev. 1.3 July 2011 Page 4 of 13 Stop (Master) Start (Master) 7 Data bits (Transmitter) 6 0 Data bit (Transmitter) Acknowledge (Receiver) SCL SDA Figure 3. Data Transfer Protocol Stop Condition A stop condition is indicated when the bus master drives SDA from low to high while the SCL signal is high. All operations using the FM24W256 should end with a stop condition. If an operation is in progress when a stop is asserted, the operation will be aborted. The master must have control of SDA (not a memory read) in order to assert a stop condition. Start Condition A start condition is indicated when the bus master drives SDA from high to low while the SCL signal is high. All commands should be preceded by a start condition. An operation in progress can be aborted by asserting a start condition at any time. Aborting an operation using the start condition will ready the FM24W256 for a new operation. If during operation the power supply drops below the specified VDD minimum, the system should issue a start condition prior to performing another operation. Data/Address Transfer All data transfers (including addresses) take place while the SCL signal is high. Except under the two conditions described above, the SDA signal should not change while SCL is high. Acknowledge The acknowledge takes place after the 8 th data bit has been transferred in any transaction. During this state the transmitter should release the SDA bus to allow the receiver to drive it. The receiver drives the SDA signal low to acknowledge receipt of the byte. If the receiver does not drive SDA low, the condition is a no-acknowledge and the operation is aborted. The receiver would fail to acknowledge for two distinct reasons. First is that a byte transfer fails. In this case, the no-acknowledge ceases the current operation so that the part can be addressed again. This allows the last byte to be recovered in the event of a communication error. Second and most common, the receiver does not acknowledge to deliberately end an operation. For example, during a read operation, the FM24W256 will continue to place data onto the bus as long as the receiver sends acknowledges (and clocks). When a read operation is complete and no more data is needed, the receiver must not acknowledge the last byte. If the receiver acknowledges the last byte, this will cause the FM24W256 to attempt to drive the bus on the next clock while the master is sending a new command such as stop. Slave Address The first byte that the FM24W256 expects after a start condition is the slave address. As shown in Figure 4, the slave address contains the device type, the device select address bits, and a bit that specifies if the transaction is a read or a write. Bits 7-4 are the device type and should be set to 1010b for the FM24W256. These bits allow other types of function types to reside on the 2-wire bus within an identical address range. Bits 3-1 are the address select bits. They must match the corresponding value on the external address pins to select the device. Up to eight FM24W256s can reside on the same two-wire bus by assigning a different address to each. Bit 0 is the read/write bit. R/W=1 indicates a read operation and R/W=0 indicates a write operation. |
Аналогичный номер детали - FM24W256-GTR |
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Аналогичное описание - FM24W256-GTR |
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