Pen Interrupt - Sharp LH79524 User Manual

LH79524/LH79525 User's Guide

2.1.8.2 Pen Interrupt

The Pen Interrupt (PENIRQ) is enabled when the settings on the bias switches are
switched to the Pen Interrupt Mode configuration and the ADC is set up to trigger a
measurement on PENIRQ. The Pen Interrupt is used by the TSC to start the state
machine. The state machine may begin a sequence of conversions, depending on
the contents of the General Configuration (GC) register, when a Pen Interrupt occurs
(see Section 2.2.2.6). PENIRQ is latched and remains HIGH until the PENIC bit of the
Interrupt Clear (IC) register is asserted (see Section 2.2.2.14). The latched value of the
Pen Interrupt is stored in the Interrupt Status register. The instantaneous raw status of the
Pen Interrupt is stored in the General Status (GS) register (see Section 2.2.2.7).
NOTE: If a measurement sequence is configured to keep the Touch Screen biased for Pen detect on every
2.1.8.3 End-of-Sequence Interrupt
The End-of-Sequence Interrupt occurs after the programmed number of conversions
(NOC) occurs. After the ADC converts all the data for a given sequence of conversions,
this interrupt goes HIGH. The End-of-Sequence Interrupt is latched and remains HIGH
until the EOSINTC bit of the IC Register is set.
2.1.8.4 FIFO Watermark Interrupt
The FIFO Watermark Interrupt occurs when the number of entries in the FIFO is greater
than or equal to the programmed watermark level FIFOWMK (GC Register, bits [6:3]). This
interrupt clears when the FIFO contents falls below the watermark level.
2.1.8.5 FIFO Overrun Interrupt
The FIFO Overrun Interrupt occurs when the receiving logic tries to place data into the
FIFO after the FIFO has been completely filled, exceeding the FIFO's maximum capacity
of 16 entries. The interrupt is cleared when the FIFO is read.
2.1.9 Application Details
An application note entitled 'Using the SHARP ADC with Resistive Touch Screens' is avail-
able from SHARP that provides more detailed application information dealing with use and
programming of the ADC.
measurement, PENIRQ is not generated on every sequence. If, on the other hand, the Pen detect
circuit is disconnected, there will be an edge every time the system enters Idle state.
Analog-to-Digital Converter/Brownout Detector
Version 1.0 2-9