CS5480 datasheet(28/70 Pages) CIRRUS

28 / 70 page

CS5480

DS980F3

The application program can change both the scale and

range of temperature by changing the Temperature

Gain (TGAIN) and Temperature Offset (TOFF) 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 |PSUM| and

|QSUM| are compared to the value in the No-Load

Threshold register (LoadMIN). If both |PSUM| and |QSUM|

are less than this threshold, then PSUM and QSUM are

forced to zero. If SSUM is less than the value in LoadMIN

5.12 Register Protection

To prevent the critical configuration and calibration

registers from unintended changes, the CS5480

provides

two

enhanced

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

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

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

loaded with the calibrations, the host microcontroller

should keep a copy of the checksum (RegChk_Copy) in

its

memory.

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

-2

Phase A Channel

-2

Phase B Channel

-2

Phase C Channel

Stop

Phase C Count

Phase B Count

Phase A Count

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

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