SBOS716D May 2015 – January 2020 TMP107
PRODUCTION DATA.
The TMP107 uses a TI proprietary, one-wire, UART-compatible, bidirectional, communication protocol called SMAART wire. It is a true one-wire communication protocol where the host can communicate with multiple daisy-chained TMP107 devices. The host device can be an off-the-shelf UART transceiver, or a microcontroller in which communication is performed by bit banging of the GPIO pins. When bit banging, follow the communication protocol format and specified parameters. All TMP107 devices have the default device addresses set to 0h.
After the devices are assembled in a daisy-chain configuration per the application requirements, the host must send the address-initialize command. This command initializes the daisy-chain so that all of the devices in the chain are assigned a unique incremental address respective to their position from the host controller (see the Address Initialize section for more information). The generated device addresses are stored in the internal EEPROM memory of each TMP107 in the chain. After the address initialization process is completed, the TMP107 devices restore their addresses from their respective EEPROM memories upon reset events.
After the daisy-chain is initialized with the address-initialize command operation, the host device can perform individual read and write operations to any device in the daisy chain by directly addressing that device. The host can also perform global read, global write, or global software reset operations on all devices in the daisy chain.
The inactive state of the bus is logic high. Every communication operation in the SMAART wire protocol consists of multiple 10-bit words. Each word is transferred least significant bit (LSB) first, with a start bit that is logic low in the beginning, a stop bit that is logic high in the end, and 8-bit data located between the start and stop bits. Each phase consists of one or more words that are transferred least significant word first. By using a start bit and stop bit for each word, the TMP107 devices can detect the start of every word and maintain synchronous communication. SMAART wire protocol communication is divided into two categories: address operations and command operations. Address operations are used to perform individual and multiple device read and write operations. Command operations are address initialize, last device polling, and global software reset operations.
Figure 18 shows the top-level phase sequences for the two types of operation. Detailed descriptions with timing diagrams are provided.