Maxim has 1-Wire chips like the DS2408 which is an 8 i/o addressable chip each with a unique 64 bit ID.
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Philips has their I2C/SMBus chips. For example, the PCA9539 is a 16 i/o chip with 2 bit ID (so only 4 devices on one I2C line).
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Are there other addressable serial busses (ie: any fieldbus like Modbus, etc.) that have all-in-one, easy-to-use, chips???