SX8674ICSTRT datasheet(21/64 Pages) SEMTECH

21 / 64 page

ADVANCED COMMUNICATIONS & SENSING

Rev 1 – 25

th July 2011

www.semtech.com

SX8674/SX8675/SX8676

Haptics Enabled Multitouch 4/5-Wire

Resistive Touchscreen Controller with Proximity Sensing

Figure 22 – Manual Mode – SELECT command (CHAN = Y; PROXSCANPERIOD = 0)

At the end of the conversion(s) bit CONVSTAT will be reset which will trigger NIRQ falling edge (if enabled in

RegIrqMsk). Host can then read channel data which will release NIRQ.

Please note that when the SELECT command is used, the channel is converted whatever the pen status (no pen

detection performed).

4.7.3

Pen Detect Mode (PENDET)

In pen detect mode (PENDET) the chip will only run pen detection (continuously when pen is up, regularly as

defined by TOUCHRATE when pen is down) and update PENSTAT bit in RegStat to be able to generate an

interrupt (NIRQ) upon pen detection and/or release. No (touch) conversion is performed in this mode.

To enter PENDET mode the host must set TOUCHRATE > 0 and then send PENDET command.

To quit PENDET mode and stop the touchscreen interface the host must enter MAN mode.

Figure 23 – Pen Detect Mode (RegIrqMsk[3:2] = 11 ; PROXSCANPERIOD = 0)

Please note that the next pen detection is not performed as long as NIRQ is low. If the host is too slow and

doesn’t read IrqSrc before next TOUCHRATE tick, no operation is performed and this TOUCHRATE tick is

simply ignored until next one.

4.7.4

Pen Trigger Mode (PENTRG)

In pen trigger mode (PENTRG) the chip will perform pen detection (continuously when pen is up, regularly as

defined by TOUCHRATE when pen is down) and if pen is down, will be followed by a conversion as defined in

RegChanMsk. The chip will update CONVSTAT bit in RegStat and will be able to generate an interrupt (NIRQ)

upon conversion completion. The chip will also update PENSTAT bit in RegStat and will be able to generate an

interrupt (NIRQ) upon pen detection and/or release.

The PENTRG mode offers the best compromise between power consumption and coordinate throughput. To

enter PENTRG mode the host must set TOUCHRATE > 0 and then send PENTRG command. To quit PENTRG

mode and stop the touchscreen interface the host must enter MAN mode.

Idle

Pen Detection

NIRQ

I2C Read RegIrqSrc

Pen Touch

Pen Release

PENSTAT

CONVSTAT

TOUCHRATE

tick

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