Data Sheet AS8168
Direction Input (DIRI)
The direction input pin (DIRI) is used to program the AS8168 for either bi-directional energy measurement, or unidirectional
measurement.
Bi-directional measurement mode ensures that all energy is measured regardless of the direction of the current through the
current sensor. In unidirectional energy measurement mode, all negative going energy is suppressed and thus excluded from
the accumulated energy value.
The programming conditions for the DIRI pin are given below:
DIRI Pin
0
1
Mode
Unidirectional
Bi-directional
The default condition, when the DIRI pin is not connected is bi-directional energy measurement, as the DIRI pin has an on-
chip pull-up resistor.
Direction Output (DIRO)
The Direction Output pin (DIRO) is a logic output providing information on the direction of the current flow through the current
sensor. The DIRO output may be used to directly drive an LED to indicate a reversal in the direction of current flow.
The conditions that will initiate a change in the DIRO logic output are given below:
If DIRI = 1 (bi-directional mode) DIRO changes only when there is a pulse at CAL or LED.
If DIRI = 0 (unidirectional mode) DIRO changes at a zero-crossing when not in anti-creep.
The timing diagram below demonstrates the operation of the DIRO output and the pulse outputs (MOP/MON, CAL and LED)
relative to the sign of the measured energy and the setting of the DIRI input.
For illustration purposes, the timing diagram below only shows the LED output.
1
2
3
4
VP
IP
DIRI
LED
DIRO
Figure 5 Timing diagram for the DIRI and DIRO functions
Revision 1.2, 11-Feb-05
Page 11 of 30