Datasheet

TEMPERATURE REGISTERS STATUS REGISTER
CONFIGURATION REGISTER 1
TMP441
TMP442
SBOS425A – DECEMBER 2008 – REVISED MARCH 2009 .............................................................................................................................................. www.ti.com
The TMP441/42 have four 8-bit registers that hold The Status Register reports the state of the
temperature measurement results. Both the local temperature ADCs. Table 4 shows the Status
channel and the remote channel have a high byte Register bits. The Status Register is read-only, and is
register that contains the most significant bits (MSBs) read by accessing pointer address 08h. The BUSY bit
of the temperature analog-to-digital converter (ADC) = '1' if the ADC is making a conversion; it is set to '0'
result and a low byte register that contains the least if the ADC is not converting.
significant bits (LSBs) of the temperature ADC result.
The local channel high byte address is 00h; the local
channel low byte address is 10h. The remote channel
Configuration Register 1 (pointer address 09h) sets
high byte is at address 01h; the remote channel low
the temperature range and controls shutdown mode.
byte address is 11h. For the TMP442, the second
The Configuration Register is set by writing to pointer
remote channel high byte address is 02h; the second
address 09h and read by reading from pointer
remote channel low byte is 12h. These registers are
address 09h. The shutdown (SD) bit (bit 6) enables or
read-only and are updated by the ADC each time a
disables the temperature measurement circuitry. If
temperature measurement is completed.
SD = '0', the TMP441/42 convert continuously at the
The TMP441/42 contain circuitry to assure that a low
rate set in the conversion rate register. When SD is
byte register read command returns data from the
set to '1', the TMP441/42 stop converting when the
same ADC conversion as the immediately preceding
current conversion sequence is complete and enters
high byte read command. This condition remains
a shutdown mode. When SD is set to '0' again, the
valid only until another register is read. For proper
TMP441/42 resume continuous conversions. When
operation, the high byte of a temperature register
SD = '1', a single conversion can be started by writing
should be read first. The low byte register should be
to the One-Shot Register.
read in the next read command. The low byte register
The temperature range is set by configuring bit 2 of
may be left unread if the LSBs are not needed.
the Configuration Register. Setting this bit low
Alternatively, the temperature registers may be read
configures the TMP441/42 for the standard
as a 16-bit register by using a single two-byte read
measurement range ( – 55 ° C to +127 ° C); temperature
command from address 00h for the local channel
conversions are stored in the standard binary format.
result, or from address 01h for the remote channel
Setting bit 2 high configures the TMP441/42 for the
result (02h for the second remote channel result).
extended measurement range ( – 55 ° C to +150 ° C);
The high byte is output first, followed by the low byte.
temperature conversions are stored in the extended
Both bytes of this read operation are from the same
binary format (see Table 1 ). The remaining bits of the
ADC conversion. The power-on reset value of all
Configuration Register are reserved and must always
temperature registers is 00h.
be set to '0'. The power-on reset value for this
register is 00h. Table 5 summarizes the bits of
Configuration Register 1.
Table 4. Status Register Format
STATUS REGISTER (Read = 08h, Write = NA)
BIT # D7 D6 D5 D4 D3 D2 D1 D0
BIT NAME BUSY 0 0 0 0 0 0 0
POR VALUE 0
(1)
0 0 0 0 0 0 0
(1) The BUSY changes to ' 1 ' almost immediately ( < 100 µ s) following power-up, as the TMP441/42 begins the first temperature conversion.
It is high whenever the TMP441/42 converts a temperature reading.
Table 5. Configuration Register 1 Bit Descriptions
CONFIGURATION REGISTER 1 (Read/Write = 09h, POR = 00h)
BIT NAME FUNCTION POWER-ON RESET VALUE
7 Reserved — 0
0 = Run
6 SD 0
1 = Shut down
5, 4, 3 Reserved — 0
0 = – 55 ° C to +127 ° C
2 Temperature Range 0
1 = – 55 ° C to +150 ° C
1, 0 Reserved — 0
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