CS5464 datasheet(22/46 Pages) CIRRUS

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CS5464

DS682F3

7. USING THE CS5464

7.1 Initialization

The CS5464 uses a power-on-reset circuit (POR) to

provide an internal reset until the analog voltage reach-

es 4.0 V. The RESET input pin can also be used by the

application circuit to reset the part.

After RESET is removed and the oscillator is stable, an

initialization program is executed to set the default reg-

ister values.

A Software Reset command is also provided to allow

the application to run the initialization program without

removing power or asserting RESET.

The application should avoid sending commands during

initialization. The DRDY bit in the Status register indi-

cates when the initialization program has completed.

7.2 Power-down States

The CS5464 has two power-down states, stand-by and

sleep. In the stand-by state, all circuitry except the volt-

age reference and crystal oscillator is powered off. In

sleep state, all circuitry except the instruction decoder is

powered off.

To return the device to the active state, send a Wake-

Up/Halt command to the device. When returning from

stand-by mode, registers will retain their contents prior

to entering the stand-by state. When returning from

sleep mode, a complete initialization occurs.

7.3 Tamper Detection and Correction

The CS5464 provides compensation for at least two

forms of meter tampering. A second current input is pro-

vided in the event that the primary input is impaired by

tampering. (See Figure 14 on page 42). An internal

RMS voltage reference is also available in the event that

the voltage input has been compromised by tampering.

Power and energy are calculated for BOTH current in-

puts (both energy channels). The CS5464 can automat-

ically choose the channel with the greater magnitude.

The register EMIN, (also called IrmsMIN) sets a minimum

level for automatic channel selection, and IchanLEVEL

sets a minimum difference that will allow a channel

change. Modes register bit Ichan selects the energy

channel, and is normally driven by the CS5464 pro-

gram. This affects the pulse registers and pulse energy

outputs. (See figure 8).

The application program can also choose the more ap-

propriate energy channel. Modes register bit Ihold dis-

ables automatic selection and Ichan can be driven by

the application. Shown below is the channel selector.

If the application detects that the voltage input has been

impaired it may choose to use the fixed internal RMS

voltage reference by setting the VFIX bit in the Modes

fault 0.707107 (full-scale RMS) but can be changed by

the application program. (See figure 9)

AVG

Figure 8. Energy Channel Selection

Figure 9. Fixed RMS Voltage Selection

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