SERIAL BUS ADDRESS
To program the ADS1112, the master must first address slave devices via a slave address byte. The slave address byte consists of seven address bits, and a direction bit indicating the intent of executing a read or write operation.
The ADS1112 features two address pins, A0 and A1, that set the I2C address. These pins can be set to a logic low, logic high, or left unconnected (floating), allowing eight
addresses to be selected with only two pins as shown in Table 4. The state of pins A0 and A1 is sampled on power-up or after an I2C general call, and should be set prior to any activity on the interface.
I2C DATA RATES
The I2C bus operates in one of three speed modes. Standard mode allows a clock frequency of up to 100kHz; fast mode permits a clock frequency of up to 400kHz; and high-speed mode (also called Hs mode), which allows a clock frequency of up to 3.4MHz. The ADS1112 is fully compatible with all three modes.
No special action needs to be taken to use the ADS1112 in standard or fast modes, but high-speed mode must be activated. To activate high-speed mode, send a special address byte of 00001xxx following the START condition, where xxx are bits unique to the Hs-capable master. This byte is called the Hs master code. (Note that this is different
from normal address bytes; the low bit does not indicate read/write status.) The ADS1112 will not acknowledge this byte; the I2C specification prohibits acknowledgment of the Hs master code. On receiving a master code, the ADS1112 will switch on its Hs mode filters, and communicate at up to 3.4MHz. The ADS1112 will switch out of Hs mode with the next STOP condition.
For more information on high-speed mode, consult the I2C specification.
I2C GENERAL CALL
The ADS1112 responds to the I2C General Call address (0000000) if the eighth bit is 0. The device will acknowledge the General Call address and respond to commands in the second byte. If the second byte is 00000100 (04h), the ADS1112 will latch the status of the address pins, A0 and A1, but not perform a reset. If the second byte is 00000110 (06h), the ADS1112 will latch the status of the address pins and reset the internal registers.
（1）第一帧（地址帧）为0 + 第二帧（命令帧）04h ：ADS1112会锁存A0，A1脚的状态
（2）第一帧（地址帧）为0 + 第二帧（命令帧）06h ：ADS1112会锁存A0，A1脚的状态并执行一次复位操作。