Host

Device

(1)

Device

(2)

Device

(N)

RX

TX

Interface Logic

Interface Logic

Interface Logic

RX

RX

RX

TX

TX

TX

Host

Device

(1)

Device

(2)

Device

(N)

RX

TX

Interface Logic

Interface Logic

Interface Logic

RX

RX

RX

TX

TX

TX

9

TMP104

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SBOS564B – NOVEMBER 2011 – REVISED DECEMBER 2018

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Each TMP104 in the chain interprets the initialization command byte and disconnects the chain, as shown in

Figure 10. The host must then send the address assignment command, consisting of P7-P4 = 1001 and P3-P0 =

0000, where P3-P0 represents the address of the first device in the chain; this word is stored internally as its

device ID. The first device increments the unit in the device address and then reconnects the bus, as shown in

Figure 11. This address is then sent to the next device in the chain. Once all devices on the chain have received

the respective addresses, the host receives the last programmed address on the chain + 1. The host can use

this information to determine the total number of devices in the chain and the respective address of each device.

After the initialization sequence, every device can be addressed individually or through global commands. This

global initialization sequence is a requirement and must be performed before any other communication.

Figure 10. TMP104 Daisy-Chain: Bus Status at Start of Address Assignment

Figure 11. TMP104 Daisy-Chain: Bus Status After First Device Address Assignment

7.3.4 Global Read and Write

The host can initiate a global read or write command to all TMP104s in the daisy-chain by sending the read/write

command, consisting of P7-P3 = 11110. P2-P1 indicate the data register pointer, as shown in Table 4, and P0

indicates read/write control. P0 = 0 indicates a global write command. The host must transfer one more byte of

data for the register (indicated by bits P2-P1), and every TMP104 in the daisy-chain updates the appropriate

register. P0 = 1 indicates a global read command. The TMP104 with the device ID of '0000' then breaks the bus

connection, transmits the data from the register indicated by bits P2-P1, and then reconnects the bus. The

TMP104 with the device ID of '0001' then repeats the same sequence, followed by the rest of the TMP104

devices in the daisy-chain.

Table 4. Pointer Addresses

P0

P0

REGISTER

0

0

Temperature register (read-only)

0

1

Configuration register (read/write)

1

0

TLOW register (read/write)

1

1

THIGH register (read/write)