Datasheet

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SBOS383C − DECEMBER 2006 − REVISED MAY 2008
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15
SOFTWARE RESET
The TMP411 may be reset by writing any value to Pointer
Register FCh. This restores the power-on reset state to all
of the TMP411 registers as well as abort any conversion
in process and clear the ALERT
and THERM pins.
The TMP411 also supports reset via the two-wire general
call address (00000000). The TMP411 acknowledges the
general call address and responds to the second byte. If
the second byte is 00000110, the TMP411 executes a
software reset. The TMP411 takes no action in response
to other values in the second byte.
CONSECUTIVE ALERT REGISTER
The value in the Consecutive Alert Register (address 22h)
determines how many consecutive out-of-limit
measurements must occur on a measurement channel
before the ALERT
signal is activated. The value in this
register does not affect bits in the Status Register. Values
of one, two, three, or four consecutive conversions can be
selected; one conversion is the default. This function
allows additional filtering for the ALERT
pin. The
consecutive alert bits are shown in Table 9.
Table 9. Consecutive Alert Register
CONSECUTIVE ALERT REGISTER
(READ = 22h, WRITE = 22h, POR = 01h)
C2 C1 C0
NUMBER OF CONSECUTIVE
OUT-OF-LIMIT MEASUREMENTS
0 0 0 1
0 0 1 2
0 1 1 3
1 1 1 4
NOTE: Bit 7 of the Consecutive Alert Register controls the
enable/disable of the timeout function. See the Timeout
Function section for a description of this feature.
THERM HYSTERESIS REGISTER
The THERM Hysteresis Register, shown in Table 11,
stores the hysteresis value used for the THERM
pin alarm
function. This register must be programmed with a value
that is less than the Local Temperature High Limit Register
value, Remote Temperature High Limit Register value,
Local THERM Limit Register value, or Remote THERM
Limit Register value; otherwise, the respective
temperature comparator will not trip on the measured
temperature falling edges. Allowable hysteresis values
are shown in Table 10. The default hysteresis value is
10°C, whether the device is operating in the standard or
extended mode setting.
Table 10. Allowable THERM Hysteresis Values
THERM HYSTERESIS VALUE
TEMPERATURE
(°C)
TH[11:4]
(STANDARD BINARY)
(HEX)
0 0000 0000 00
1 0000 0001 01
5 0000 0101 05
10 0000 1010 0A
25 0001 1001 19
50 0011 0010 32
75 0100 1011 4B
100 0110 0100 64
125 0111 1101 7D
127 0111 1111 7F
150 1001 0110 96
175 1010 1111 AF
200 1100 1000 C8
225 1110 0001 E1
255 1111 1111 FF
BUS OVERVIEW
The TMP411 is SMBus interface-compatible. In SMBus
protocol, the device that initiates the transfer is called a
master, and the devices controlled by the master are
slaves. The bus must be controlled by a master device that
generates the serial clock (SCL), controls the bus access,
and generates the START and STOP conditions.
To address a specific device, a START condition is
initiated. START is indicated by pulling the data line (SDA)
from a high to low logic level while SCL is high. All slaves
on the bus shift in the slave address byte, with the last bit
indicating whether a read or write operation is intended.
During the ninth clock pulse, the slave being addressed
responds to the master by generating an Acknowledge
and pulling SDA low.
Data transfer is then initiated and sent over eight clock
pulses followed by an Acknowledge bit. During data
transfer SDA must remain stable while SCL is high,
because any change in SDA while SCL is high is
interpreted as a control signal.
Once all data has been transferred, the master generates
a STOP condition. STOP is indicated by pulling SDA from
low to high, while SCL is high.