sx8675iwltrt Semtech Corporation, sx8675iwltrt Datasheet - Page 22

• Manufacturer Part Number: sx8675iwltrt
• Description: Haptics Enabled Multitouch 4/5-wire Resistive Touchscreen Controller With Proximity Sensing
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
Please note that to prevent data loss, the next pen detection and conversion are not performed as long as all
current channel data (i.e. channels selected in RegChanMsk) have not been read. If the host is too slow and
doesn’t read all channel data before next TOUCHRATE tick, no operation is performed and this TOUCHRATE
tick is simply ignored until next one.
4.7.5
In PENTRG mode the TOUCHRATE parameter is used to define the required coordinate’s throughput/rate.
However, as previously mentioned, in order for a new conversion to be performed the current conversion must
be completed and all relevant channel data must have been read by the host. If this condition is not met when
the next TOUCHRATE tick occurs, the tick is ignored and the condition checked again at the next one. This will
result in reduced actual rate vs what has been programmed in the TOUCHRATE parameter.
This is illustrated in figures below.
Rev 1 – 25
CONVSTAT
NIRQ
I2C Read Channel
PENSTAT
TOUCHRATE
Idle
Pen Detection
tick
NIRQ
I2C Read Channel
TOUCHRATE
Maximum Throughput vs. TOUCHRATE setting
th
tick
Idle
July 2011
Figure 24 – Pen Trigger Mode (RegIrqMsk[3:2] = 10 ; PROXSCANPERIOD = 0)
Pen Detection
Touch Conversion
Pen Touch
Tconv
Trate
Figure 25 – Correct TOUCHRATE setting
Tcom
Touch Conversion
=
Resistive Touchscreen Controller with Proximity Sensing
22
SX8674/SX8675/SX8676
Pen Release
Haptics Enabled Multitouch 4/5-Wire
=> Actual rate = TOUCHRATE
Tconv+Tcom < Trate
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