DA6505.005
11 June 2018
FUNCTIONAL DESCRIPTION (continued)
Reading measurement results
MAS6505 pressure and temperature measurement
results are 24-bit unsigned numbers each of which
are stored into three 8-bit result registers. The
pressure result addresses are MSB byte (F1HEX),
LSB byte (F2HEX) and XLSB byte (F3HEX). The
temperature result addresses are MSB byte (F4HEX),
LSB byte (F5HEX) and XLSB byte (F6HEX).
MAS6505 A/D conversion and result status can be
monitored from Status register (F0HEX) which
contains RDYT and RDYP flags to indicate when
there are unread temperature (T) and/or pressure
(P) measurement results available in the pressure
and temperature result registers. See figure 2 and
table 7. The corresponding RDYx (x=T or P) flag is
set (1) when a new measurement is ready for a read.
Reading the measurement result will clear (0) the
corresponding RDYx (x=T or P) flag.
and/or RDYP flags) have been set high. This method
can be used in both forced and normal modes. In
forced mode an another choice is to wait at least
maximum A/D conversion time before reading the
result. See also figure 3 for Calibrated MAS6505
sensor system measurement flow. In normal mode it
is also possible to read results at a rate when new
results are expected to be ready. This is possible
since MAS6505 has internal A/D conversion result
memory buffer. If new result is finished during read
of result registers the new value is updated result
registers only after the serial bus communication has
been released. Important note: In normal mode
the results must be always read using
incremental read (all three bytes of each result or
all six bytes of both results at single read sequence)
to maintain A/D conversion data consistency. See
table 15 example of the incremental read in chapter
2-wire serial data interface (I2C bus). The
incremental read is recommended to be used also in
the forced mode.
The decision when to read measurement results can
be made by polling the Status register and waiting
until the flag(s) of selected measurement(s) (RDYT
Measurement start by setting MODE=01 or 10
Forced mode
temperature
or pressure
RDYT or RDYP
flag set
time
T or P
.
Measurement start by setting MODE=01 or 10
Forced mode
temperature
and pressure
RDYT
flag set
RDYP
flag set
T P
x
.
time
Measurement start by setting MODE=11
Normal mode
temperature
or pressure
RDYT or RDYP
flag set
RDYT or RDYP
flag set
DELAY setting
T or P
.
T or P
.
T or P…
DELAY setting
time
Measurement start by setting MODE=11
Normal mode
temperature
and pressure
RDYT
flag set
RDYP
flag set
RDYT
flag set
RDYP
flag set
DELAY setting
T P
x
.
T P
x
.
time
...
Figure 2. Forced and normal mode measurement and status register RDYT and RDYP flag update timing
(T=temperature, P=pressure)
10 (44)
MAS [ MICRO ANALOG SYSTEMS ]
