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STA002 数据表(PDF) 7 Page - STMicroelectronics |
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STA002 数据表(HTML) 7 Page - STMicroelectronics |
7 / 43 page for synchronisation. The STA002 is always a slave device in all its communications. 1. 1 COMMUNICATION PROTOCOL 1.1.0 Data transition or change Data changes on the SDA line must only occur when the SCL clock is low. SDA transitions while the clock is high are used to identify START or STOP condition. 1.1.1 Start condition START is identified by a high to low transition of the data bus SDA signal while the clock signal SCL is stable in the high state. A START condi- tion must precede any command for data transfer. 1.1.2 Stop condition STOP is identified by low to high transition of the data bus SDA signal while the clock signal SCL is stable in the high state. A STOP condition termi- nates communications between STA002 and the bus master. 1.1.3 Acknowledge bit An acknowledge bit is used to indicate a success- ful data transfer. The bus transmitter, either mas- ter or slave, will release the SDA bus after send- ing 8 bits of data. During the 9th clock pulse the receiver pulls the SDA bus low to acknowledge the receipt of 8 bits of data. Some registers do not give acknowledge when the data is not available. 1.1.4 Data input During the data input the STA002 samples the SDA signal on the rising edge of the clock SCL. For correct device operation the SDA signal has to be stable during the rising edge of the clock and the data can change only when the SCL line is low. 1.2 DEVICE ADDRESSING To start communication between the master and the STA002, the master must initiate with a start condition. Following this the master sends onto the SDA line 8 bits (MSB first) corresponding to the device select address and read or write mode. The 7 most significant bits are the device address identifier, corresponding to the I2C bus definition. For the STA002 these are fixed as 1101010. The 8th bit (LSB) is the read or write operation bit (RW; set to 1 in read mode and to 0 in write mode). After a START condition the STA002 identifies on the bus the device address and if matching it will acknowledges the identification on SDA bus during the 9th bit time. The following 2 bytes after the device identifica- tion byte are the internal space address. 1.3 WRITE OPERATION (see fig. 5) Following a START condition the master sends a device select code with the RW bit set to 0. The STA002 gives the acknowledge and waits for the 2 bytes of internal address. The least signifi- cant 10 bits of the 2 bytes address provides ac- cess to any of the internal registers. The most significant bit means incremental mode (1 = autoincremental, 0 = no) and the other bits are set to zero. After the receiption of each of the internal bytes address the STA002 again responds with an ac- knowledge. 1.3.1 Byte write In the byte write mode the master sends one data byte and this is acknowledged by STA002. The master then terminates the transfer by generating a STOP condition. 1.3.2 Multibyte write The multibyte write mode can start from any inter- nal address. The master sends the data and each one is acknowledged by the STA002. The trans- fer is terminated by the master generating a STOP condition. 1.4 READ OPERATION (see Fig. 6) 1.4.1 Current byte address read The STA002 has an internal byte address counter. Each time a byte is written or read, this counter, according to the autoincremental bit set- ting, is incremented or not. For the current byte address read mode, follow- ing a START condition the master sends the de- vice address with the RW bit set to 1. The STA002 acknowledges this and outputs the byte addressed by the internal byte address counter. The counter is then incremented or not depend- ing on the autoincremental bit. The master does not acknowledge the received byte, but termi- nates the transfer with a STOP condition. 1.4.2 Random byte address read A dummy write is performed to load the byte ad- dress into the internal address register. STA002 7/43 |
类似零件编号 - STA002 |
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类似说明 - STA002 |
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