AS8218 datasheet(62/123 Pages) AMSCO

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Data Sheet AS8218 / AS8228

Revision 3.0, 31-May-06

Page 62 of 123

Timing:

COUNT

led

Gate

refp

counted refp

CINT

Notes:

1) The COUNT signal is synchronized with ‘led’.

2) COUNT is reset and CINT is set using clk and checking for falling edge on Gate.

3) The PCNT register is only updated when counting is finished.

Example:

Select IO3 as the pulse reference input.

Meter is 220Vmains; Imax = 20A

Meter constant: 1,600imp/kWh

Reference meter constant: 16 million imp/kWh

MPIO

SET_EN0

(9505h):

IO3 bit = 0 (output disabled)

SEL_IN_REFP

(950Ch):

02h

DSP

mconst

(9330h):

07h

(Ideal) Pulse_lev (932Ch – 932Ah) =

220

230

950

570

= 1,193,804

⇒ 12374Ch

⇒ 932Ah: 4Ch

932Bh: 37h

932Ch: 12h

Procedure:

Status1 (951Fh): 80h

→ starts pulse counting.

When pulse counting is completed

→ CINT bit in Status1 = 1.

The status of the CINT bit in Status1 may be checked to confirm that the pulse counting is complete.

Alternatively, the time between 2 pulses may be calculated to determine the count cycle time (the first pulse is

used for synchronization and the second pulse starts the count cycle).

Following the pulse counting cycle, the number of pulses counted can be read from PCNT0/PCNT1/PCNT2

(951Bh/951Ch/951Dh).

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