AV /2
CC
ESIDVCC
Undamped Oscillation
Undamped Envelopes
Damped Envelopes
Damped Oscillation
Time
ESI Operation
986
SLAU367P – October 2012 – Revised April 2020
Copyright © 2012–2020, Texas Instruments Incorporated
Extended Scan Interface (ESI)
37.2.7.3 ESIIV, Interrupt Vector Generator
The ESIIFGx interrupt flags are prioritized and combined to source a single interrupt vector. The interrupt
vector register ESIIV is used to determine which flag requested an interrupt.
The highest-priority enabled interrupt generates a number in the ESIIV register (see register description).
This number can be evaluated or added to the program counter to automatically enter the appropriate
software routine. Disabled ESI interrupt do not affect the ESIIV value.
A read access of the ESIIV register automatically resets the highest-pending interrupt flag. If another
interrupt flag is set, another interrupt is immediately generated after servicing the initial interrupt. For
example, if the ESICNT1 (ESIIFG3) and ESICNT2 (ESIIFG4) interrupt flags are set when the interrupt
service routine accesses the ESIIV register, ESIIFG3 is reset automatically. After the RETI instruction of
the interrupt service routine is executed, the ESIIFG4 interrupt flag generates another interrupt.
A write access to the ESIIV register clears all pending ESI interrupt flags.
37.2.8 Overview of ESI Applications
The ESI supports different types of sensors. This chapter introduces only a few of the existing solutions of
how to use the ESI.
37.2.8.1 Using the ESI with LC Sensors
Systems with LC sensors use a disk that is partially covered with a damping material to measure rotation.
Rotation is measured with LC sensors by exciting the sensors and observing the resulting oscillation. The
oscillation is either damped or un-damped by the rotating disk. The oscillation is always decaying because
of energy losses but it decays faster when the damping material on the disk is within the field of the LC
sensor, as shown in
. The LC oscillations can be measured with the oscillation test or the
envelope test.
Figure 37-15. LC Sensor Oscillations