Cirrus Logic CS5480 - Manual (Page 28)

CS5480
28 DS980F3
The application program can change both the scale and
range of temperature by changing the Temperature
Gain (T
GAIN
) and Temperature Offset (T
OFF
) registers.
T updates every 2240 output word rate (OWR) samples.
The Status0 register bit TUP indicates when T is updat-
ed.
5.11 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.
5.12 Register Protection
To prevent the critical configuration and calibration
registers from unintended changes, the CS5480
provides two enhanced register protection
mechanisms: write protection and automatic checksum
calculation.
5.12.1 Write Protection
Setting the DSP_LCK[4:0] bits in the RegLock register
to 0x16 enables the CS5480 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 CS5480 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 31, 6.3 Software Registers
Summary (Page 16) on page 33, and 6.4 Software
Registers Summary (Page 17) on page 35.
5.12.2 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 31, 6.3
Software Registers Summary (Page 16) on page 33,
and 6.4 Software Registers Summary (Page 17) on
page 35. 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 CS5480 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 CS5480 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 19. Phase Sequence C, B, A for Rising Edge Transition