CS5490 datasheet(23/56 Pages) APEX

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CS5490

DS982F2

5.8 Temperature Measurement

The CS5490 has an internal temperature sensor, which

is designed to measure temperature and optionally

compensate for temperature drift of the voltage

reference. Temperature measurements are stored in

the temperature register (T), which, by default, is

configured to a range of ±128°C.

The application program can change the scale and

range of the temperature (T) register by changing the

temperature gain (TGAIN) register and temperature

offset (TOFF) register.

The temperature (T) register updates every 2240 output

word rate (OWR) samples. The Status0 register bit TUP

indicates when T is updated.

5.9 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

(LoadMin) register. 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 register,

then SSum is forced to zero.

5.10 Register Protection

To prevent the critical configuration and calibration

registers from unintended changes, the CS5490 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 CS5490 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 CS5490 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 26, 6.3 Software Registers

Summary (Page 16) on page 28, and 6.4 Software

Registers Summary (Page 17) on page 29.

5.10.2 Register Checksum

All the configuration and calibration registers are

protected by checksum, if enabled. Refer to sections 6.2

Hardware Registers Summary (Page 0) on page 26, 6.3

Software Registers Summary (Page 16) on page 28,

and 6.4 Software Registers Summary (Page 17) on

page 29. The checksum for all registers marked with an

asterisk symbol (*) is computed at the rate of OWR. The

checksum result is stored in the RegChk register. After

the CS5490 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 CS5490 is

necessary.

The automatic checksum computation can be disabled by

setting the REG_CSUM_OFF bit in the Config2 register.

-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 13. Phase Sequence C, B, A for Rising Edge Transition

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