Datasheet

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SBOS371A − AUGUST 2006 − REVISED OCTOBER 2007
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12
CONFIGURATION REGISTER
The Configuration Register sets the temperature range,
controls Shutdown mode, and determines how the
ALERT/THERM2 pin functions. The Configuration
Register is set by writing to pointer address 09h and read
by reading from pointer address 03h.
The MASK bit (bit 7) enables or disables the ALERT
pin
output if AL/TH = 0. If AL/TH = 1 then the MASK bit has no
effect. If MASK is set to ‘0’, the ALERT pin goes low when
one of the temperature measurement channels exceeds
its high or low limits for the chosen number of consecutive
conversions. If the MASK bit is set to ‘1’, the TMP401
retains the ALERT
pin status, but the ALERT pin will not
go low.
The shutdown (SD) bit (bit 6) enables or disables the
temperature measurement circuitry. If SD = 0, the TMP401
converts continuously at the rate set in the Conversion
Rate Register. When SD is set to ‘1’, the TMP401
immediately stops converting and enters a shutdown
mode. When SD is set to ‘0’ again, the TMP401 resumes
continuous conversions. A single conversion can be
started when SD = 1 by writing to the One-Shot Register.
The AL/TH bit (bit 5) controls whether the ALERT
pin
functions in ALERT mode or THERM2 mode. If AL/TH = 0,
the ALERT pin operates as an interrupt pin. In this mode, the
ALERT
pin goes low after the set number of consecutive
out-of-limit temperature measurements occur.
If AL/TH = 1, the ALERT
/THERM2 pin implements a
THERM function (THERM2
). In this mode, THERM2
functions similar to the THERM pin except that the local
high limit and remote high limit registers are used for the
thresholds. THERM2
goes low when either RHIGH or
LHIGH is set.
The temperature range is set by configuring bit 2 of the
Configuration Register. Setting this bit low configures the
TMP401 for the standard measurement range (0°C to
+127°C); temperature conversions will be stored in the
standard binary format. Setting bit 2 high configures the
TMP401 for the extended measurement range (−55°C to
+150°C); temperature conversions will be stored in the
extended binary format (see Table 1).
The remaining bits of the Configuration Register are
reserved and must always be set to ‘0’. The power-on reset
value for this register is 00h. Table 5 summarizes the bits
of the Configuration Register.
Table 5. Configuration Register Bit Descriptions
CONFIGURATION REGISTER (Read = 02h, Write = NA)
BIT NAME FUNCTION POWER-ON RESET VALUE
7 MASK
0 = ALERT Enabled
1 = ALERT Masked
0
6 SD
0 = Run
1 = Shut Down
0
5 AL/TH
0 = ALERT Mode
1 = THERM Mode
0
4, 3 Reserved — 0
2 Temperature Range
0 = 0°C to +127°C
1 = −55°C to +150°C
0
1, 0 Reserved — 0