78M6612-IMSLASHFSLASHP datasheet(84/111 Pages) TERIDIAN

84 / 111 page

78M6612 Data Sheet

DS_6612_001

Rev. 1.2

must be 12 (allowing for one settling cycle). The required configuration is FIR_LEN = 1 (three cycles per

conversion) and MUX_DIV[1:0] = 01 (4 conversions per mux frame).

During operation, the MPU is in charge of controlling the multiplexer cycles, for example by inserting an

alternate multiplexer sequence at regular intervals using MUX_ALT. This enables temperature

measurement. The polarity of chopping circuitry must be altered for each sample. It must also alternate

for each alternate multiplexer reading. This is accomplished by maintaining CHOP_E = 00.

4.4.5

CE Calculations

The CE performs the precision computations necessary to accurately measure energy. These

computations include offset cancellation, products, product smoothing, product summation, frequency

detection, VAR calculation, sag detection, peak detection, and voltage phase measurement. Refer to the

applicable 78M6612 Firmware Description Document.

4.4.6

CE Status

Since the CE_BUSY interrupt occurs at 2520.6 Hz, it is desirable to minimize the computation required

in the interrupt handler of the MPU. The MPU can read the CE status word at every CE_BUSY interrupt.

Address

Name

0x70

Description

CESTATUS

See description of CE status word below.

The CE Status Word is used for generating early warnings to the MPU. It contains sag warnings for VA

as well as F0, the derived clock operating at the fundamental input frequency. CESTATUS provides

information about the status of voltage and input AC signal frequency, which are useful for generating

early power fail warnings, e.g. to initiate necessary data storage. CESTATUS represents the status flags

for the preceding CE code pass (CE busy interrupt). Sag alarms are not remembered from one code

pass to the next. The CE Status word is refreshed at every CE_BUSY interrupt.

The significance of the bits in CESTATUS is shown in the table below:

CESTATUS

[bit]

Name

Description

31-29

Not Used

These unused bits will always be zero.

F0 is a square wave at the exact fundamental input frequency.

Reserved

SAG_B

Normally zero. Becomes one when VB remains below SAG_THR for

SAG_CNT samples. Will not return to zero until VB rises above SAG_THR.

SAG_A

Normally zero. Becomes one when VA remains below SAG_THR for

SAG_CNT samples. Will not return to zero until VA rises above SAG_THR.

24-0

Not Used

These unused bits will always be zero.

78M6612-IM/F/P Datasheet(PDF) 84 Page - Teridian Semiconductor Corporation

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