Data Sheet AS8168

Revision 1.2, 11-Feb-05

Page 13 of 30

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Normal Operation Mode: Normal operation is the mode in which the device operates to perform the kWh metering

function, for which the device is designed.

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Programming Mode: Programming is the mode in which the AS8168 is set to perform the programming operations. When

in Programming mode, two different operations may be carried out:

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Test Write: Test Write enables the writing of data to a register in the device and for the resultant chip behaviour to be

investigated, before the data is written permanently to the non-volatile PROM (programmable read only memory)

memory.

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Burn: Burn is the programming cycle that ensures that the required data is permanently written to the non-volatile

PROM (programmable read only memory).

During Programming mode all pulse outputs (MOP/MON, CAL and LED) can be accessed.

The AS8168 may only be set up in one of these two modes during the ‘power up’ cycle of the device. The mode is selected

by programming the TM and DIRO at ‘power up’ as shown in the table below:

Mode of Operation

TM

DIRO

Normal Operation

0

X

Programming

1

0

Note: Pin DIRO has an on-chip internal pull-down resistor, thus the pin may be left open or tied ‘low’ for both Normal

Operation and Programming modes. The default mode is thus Normal Operation mode, with the AS8168 only being set to

Programming mode when TM is pulled high during power up.

The analog input pin PROG is also required for the programming of the AS8168. During Test-Write PROG is used to transfer

digital data to the internal register. During Burn it is used to change the states of the internal PROM cells.

When in Programming mode, the AS8168 must be powered down before the device can enter Normal Operation mode.

PROM Definition and Contents

The table below provides a definition of the internal PROM cells. As shown, sets of PROM cells form binary words, which

represent, for example, a defined pulse rate.

Parameter

Description

Number

of bits

Register bits

Settings

Default

Bank 0

Bank 1

Gain

Select current

channel gain

2

[34:33]

[67:66]

00 : 4

01 : 16

10 : 16

11 : 20

11

Acreep_sel

Select anti creep

threshold

2

[32:31]

[65:64]

00 : 2.32mA

01 : 7.43mA

10 : 14.9mA

11 : 29.7mA

01

F_mon_sel

Select MOP/MON

pulse rate

[imp/kWh]

2

[30:29]

[63:62]

00 : 100

01 : 200

10 : 400

11 : 800

10