DS1821
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CONFIGURATION REGISTER BIT DESCRIPTIONS Table 3
Bit Name
(User Access)
Functional Description
DONE — Temperature Conversion Done
(Read Only)
DONE = 0 — Temperature conversion is in progress.
DONE = 1 — Temperature conversion is complete.
NOTE: DONE = 0 at POR.
NVB — Non-volatile Memory Busy
(Read Only)
NVB = 0 — Nonvolatile memory is not busy.
NVB = 1 — A write to EEPROM memory is in progress
THF* — Temperature High Flag
(Read/Write)
THF = 0 — The measured temperature has not exceeded the
value stored in the T
H
register.
THF = 1 — At some point in time the measured temperature has
been higher than the value stored in the T
H
register. THF will
remain a 1 until it is over-written with a 0 by the user.
TLF* — Temperature Low Flag
(Read/Write)
TLF = 0 — The measured temperature has not been lower than
the value stored in the T
L
register.
TLF = 1 — At some point in time the measured temperature has
been lower than the value stored in the T
L
register. TLF will
remain a 1 until it is over-written with a 0 by the user.
T/R¯* — Power-up Operating Mode
(Read/Write)
T/R¯ = 0 — DS1821 powers up in 1- wire mode.
T/R¯ = 1 — DS1821 powers up in thermostat mode.
POL* — Thermostat Output (DQ) Polarity
(Read/Write)
POL = 0 — Thermostat output (DQ) is active low.
POL = 1 — Thermostat output (DQ) is active high.
1SHOT* — Conversion Mode
(Read/Write)
1SHOT = 0 — Continuous conversion mode. The Start Convert
T [EEh] command initiates continuous temperature conversions,
which can be stopped with the Stop Convert T [22h] command.
1SHOT = 1 — One-shot mode. The Start Convert T [EEh]
command initiates a single temperature conversion after which
the DS1821 returns to a low-power standby state.
*Stored in EEPROM
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