TMP451 datasheet(15/42 Pages) TI2

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TMP451

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SBOS686A – JUNE 2013 – REVISED DECEMBER 2014

Programming (continued)

7.5.1.5 Time-out Function

If the SMBus time-out function is enabled, the TMP451 device resets the serial interface if either SCL or SDA are

held low for 25 ms (typical) between a START and STOP condition. If the TMP451 device is holding the bus low,

the device releases the bus and waits for a START condition. To avoid activating the time-out function,

maintaining a communication speed of at least 1 kHz for the SCL operating frequency is necessary. The SMBTO

bit (bit 7) of the consecutive ALERT register controls the time-out enable. Setting the SMBTO bit to a value of 0

(default) disables the time-out. Setting the SMBTO bit to a value of 1 enables the function.

7.5.1.6 High-speed Mode

For the two-wire bus to operate at frequencies above 1 MHz, the master device must issue a high-speed mode

(Hs-mode) master code (0000 1xxx) as the first byte after a START condition to switch the bus to high-speed

operation. The TMP451 device does not acknowledge this byte, but switches the input filters on SDA and SCL

and the output filter on SDA to operate in Hs-mode, allowing transfers at up to 2.5 MHz. After the Hs-mode

master code has been issued, the master transmits a two-wire slave address to initiate a data transfer operation.

The bus continues to operate in Hs-mode until a STOP condition occurs on the bus. Upon receiving the STOP

condition, the TMP451 device switches the input and output filters back to fast mode operation.

7.5.1.7 General Call Reset

The TMP451 device supports reset using the two-wire general call address 00h (0000 0000b). The TMP451

device acknowledges the general call address and responds to the second byte. If the second byte is 06h (0000

0110b), the TMP451 device executes a software reset. This software reset restores the power-on reset state to

all TMP451 registers, and it aborts any conversion in progress. The TMP451 device takes no action in response

to other values in the second byte.

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