Datasheet LTC4318 (Analog Devices) - 7

LTC4318
operaTion
SCLIN to SCLOUT while N2 connects SDAIN to SDAOUT. The LTC4318 is an I2C/SMBus address translator. It bridges In most conditions, N1 and N2 stay on so that the input two segments of an I2C bus, reading incoming addresses and output buses are connected. on the master side and retransmitting them to the slave side with the 7-bit I2C addresses translated in real time. Translation starts when the master issues a START bit This allows multiple I2C devices with the same address (SDAIN goes low while SCLIN is high). The LTC4318 to be connected to the same bus without interference. turns off N2 to disconnect SDAIN from SDAOUT. As the The translated addresses are configured with external master sends the address byte, the LTC4318 translates resistors, and no extra software is required. An ENABLE the incoming address at the SDAIN pin to a new address pin allows bus segments to be enabled and disabled, and at the SDAOUT pin by XORing each incoming bit with the LTC4318 allows hot swapping isolated bus segments a user-configurable translation byte, one bit at a time. together. N3 turns on and off to send out the new address to the SDAOUT pin. Once all 7 bits of the address are processed, Figure 1 shows an I2C master connected to the input bus the LTC4318 turns on N2 again to reconnect SDAIN to of the LTC4318 (SCLIN and SDAIN). The slave devices SDAOUT. The master then transmits the R/W bit directly requiring address translation are connected to the output to the slave. If the new, translated address on SDAOUT bus of the LTC4318 (SCLOUT and SDAOUT). Any other matches the slave’s address, the slave pulls SDAOUT low slave devices that do not require address translation are to acknowledge (ACK bit). N2 remains on and the rest of placed together with the master on the input bus of the the data bytes are transmitted unmodified between the LTC4318. Two switches (N1 and N2) inside the LTC4318 master and slave. The address translation process restarts connect the input bus to the output bus. N1 connects when the master issues a new START bit. VCC1 VCC2 LTC4318 SCLIN N1 SCLOUT SLAVE MASTER #1 SDAIN N2 SDAOUT CMP2 + N3 SLAVE #2 XOR 1.8V – 0 0 0 0 0 1 0 ENABLE 7-BIT ADDRESS ADDRESS TRANSLATION TRANSLATION BYTE SHIFT REGISTER 4318 F01
Figure 1. Basic Functions of the LTC4318
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