Cirrus Logic CS5484 - Manual (Page 26)

CS5484
26 DS981F3
The temperature sensor and V2 input share the same
delta-sigma modulator on the second voltage channel.
By default, the temperature measurement is disabled,
and the delta-sigma modulator is used for V2
measurement. To enable temperature measurement,
set Config0 register bit 23, bit 22, and bit 13.
The Temperature register (T) updates every 2240
output word rate (OWR) samples. The Status0 register
bit TUP indicates when T is updated. The temperature
measurement and the second voltage channel, V2,
share the same delta-sigma modulator, so the V2
measurement will be using the V1 delta-sigma
modulator output when temperature measurement is
enabled.
5.9 Anti-creep
The anti-creep (no-load threshold) is used to determine
if a no-load condition is detected. The |P
Sum
| and |Q
Sum
|
are compared to the value in the No-Load Threshold
register (Load
MIN
). If both |P
SUM
| and |Q
SUM
| are less
than this threshold, then P
SUM
and Q
SUM
are forced to
zero. If S
SUM
is less than the value in Load
MIN
register,
then S
SUM
is forced to zero.
5.10 Register Protection
To prevent the critical configuration and calibration
registers from unintended changes, the CS5484
provides two enhanced register protection
mechanisms: write protection and automatic checksum
calculation.
5.10.1 Write Protection
Setting the DSP_LCK[4:0] bits in the RegLock register
to 0x16 enables the CS5484 DSP lockable registers to
be write-protected from the calculation engine. Setting
the DSP_LCK[4:0] bits to 0x09 disables the
write-protection mode.
Setting the HOST_LCK[4:0] bits in the RegLock register
to 0x16 enables the CS5484 HOST lockable registers to
be write-protected from the serial interface. Setting the
HOST_LCK[4:0] bits to 0x09 disables the
write-protection mode.
For registers that are DSP lockable, HOST lockable, or
both, refer to sections
6.2 Hardware Registers
Summary (Page 0) on page 29, 6.3 Software Registers
Summary (Page 16) on page 31, and 6.4 Software
Registers Summary (Page 17) on page 33.
5.10.2 Register Checksum
All the configuration and calibration registers are
protected by checksum, if enabled. Refer to
6.2
Hardware Registers Summary (Page 0) on page 29, 6.3
Software Registers Summary (Page 16) on page 31,
and 6.4 Software Registers Summary (Page 17) on
page 33. The checksum for all registers marked with an
asterisk symbol
(*) is calculated once every low-rate
cycle. The checksum result is stored in the RegChk
register. After the CS5484 has been fully configured and
loaded with the calibrations, the host microcontroller
should keep a copy of the checksum (RegChk_Copy) in
its memory. In normal operation, the host
microcontroller can read the RegChk register and
compare it with the saved copy of the RegChk register.
If the two values mismatch, a reload of configurations
and calibrations into the CS5484 is necessary.
The automatic checksum computation can be disabled
by setting the REG_CSUM_OFF bit in the Config2
register.
-2
0
2
Phase A Channel
-2
0
2
Phase B Channel
-2
0
2
Phase C Channel
Stop
Stop
Stop
Phase C Count
Phase B Count
Phase A Count
A B
C
Write 0x16 to
PSDC Register
Start on the Falling
Edge on the RX Pin
Figure 17. Phase Sequence C, B, A for Rising Edge Transition