Datasheet

Temperature Error Handling
The temperature measurement unit can detect open and/
or short-circuit temperature probes. If the resultant tem-
perature reading in less than 8µs, then the MAX35101
writes a value of 0000h to the corresponding Results
registers to indicate a short-circuit temperature probe. If
the measurement process does not discharge the TC pin
below the threshold of the internal temperature compara-
tor within 2µs of the time set by the PORTCYC[1:0] bits
in the Event Timing 2 register, then an open circuit tem-
perature probe error is declared. The MAX35101 writes a
value of FFFFh to the corresponding results registers to
indicate an open circuit temperature probe, the TO bit in
the Interrupt Status register is set, and the INT pin asserts
(if enabled). If the temperature measurement error is
caused by any other problems, then the MAX35101 writes
a value of FFFFh to each of the temperature port results
registers indicating that all of the temperature port mea-
surements are invalid.
Event Timing Operation
The event timing mode of operation is an advanced
feature that allows the user to configure the MAX35101
to perform automatic measurement cycles. This allows
the host microcontroller to enter low-power mode and
only awaken upon assertion of the MAX35101 INT pin
(if enabled) when new measurement data is available.
By using the TOF_DIFF and temperature commands
and configuring the appropriate TOFx registers and the
Event Timing registers, the event timing modes directs
the MAX35101 to provide complete data for a sequence
of measurements captured on a cyclical basis. There are
three versions of the EVTMG commands.
● EVTMG2: Performs automatic TOF_DIFF measure-
ments. The parameters and operation of the TOF
measurement are described in the Time-of-Flight
(TOF) Measurement Operations section.
● EVTMG3: Performs automatic Temperature mea-
surements. The parameters and operation of the
Temperature measurements are described in the
Temperature Measurement Operations section.
● EVTMG1: Performs automatic TOF_DIFF and
Temperature measurements.
Continuous Event Timing Operation
The MAX35101 can be configured to continue run-
ning event timing sequences at the completion of any
sequence. If the ET_CONT bit in the Calibration and
Control register is set, the currently executing EVTMGx
command continues to execute until a HALT command
is received by the MAX35101. If the ET_CONT bit is
clear, automatic execution of event timing stops after the
completion of a full sequence of measurements.
Continuous Interrupt Timing Operation
When operating in event timing mode, the INT pin can be
asserted (if enabled) either after each TOF or tempera-
ture measurement, or at the completion of the sequence
of measurements. If the CONT_INT bit in the Calibration
and Control register is set to a 1, then the INT pin asserts
(if enabled) at the completion of each TOF or temperature
command. This allows the host microcontroller to interro-
gate the current event for accuracy of measurement. If the
CONT_INT bit is set to a 0, then the INT pin only asserts
(if enabled) at the completion of a sequence of measure-
ments. This allows the host microcontroller to remain in a
low-power sleep mode and only wake-up upon the asser-
tion of the INT pin.
Error Handling During Event Timing Operation
During execution of event timing modes, any error that
occurs during a TOF_DIFF or temperature measurement
are handled as described in the corresponding error
handling sections. Calibration can be executed during
event timing operation, if programmed to do so with the
calibration configuration bits in the Calibration and Control
register. If a calibration error occurs, this is handled as
described in the Error Handling During Calibration sec-
tion. If any of these errors occur, the event timing opera-
tion does not terminate, but continues operation.
When making TOF measurements in event timing mode,
the MAX35101 provides additional data in the TOF_
Cycle_Count/TOF_Range register that can be used to
check the validity of all of the TOF measurements. The
TOF_Cycle_Count is the number of valid error-free TOF
measurements that were recorded during an Event Timing
Sequence. If a TOF error occurs, the TOF_Cycle_Count
register will not be incremented. The TOF_Range is the
range of all valid TOF measurements that were captured
during a sequence.
When making temperature measurements in event tim-
ing mode, the MAX35101 provides additional data in the
Temp_Cycle_Count register. This count increments after
every valid error-free temperature measurement and can
be used to check the validity of all of the temperature
measurements. Also, the Temperature Average Results
registers, TxAVG, are not updated with the error measure-
ment if a temperature error occurs during event timing
operation.
MAX35101 Time-to-Digital Converter with Analog Front-End
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