TSC2005
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SBAS379–DECEMBER 2006
Conversion Controlled by TSC2005 Initiated by Host (TSMode 2)
In TSMode 2, the TSC2005 detects when the touch panel is touched and causes the internal Pen-Touch signal
to activate, which lowers the PINTDAV output, if it is programmed as PENIRQ. The host recognizes the interrupt
request, and then writes to the A/D Converter Control register to select one of the two touch screen scan
functions:
1. X-Y-Z Scan (converter function select bits C[3:0] = Control Byte 1 D[6:3] = 0000); or
2. X-Y Scan (converter function select bits C[3:0] = Control Byte 1 D[6:3] = 0001).
See Table 7 for more information on the converter function select bits.
The conversion process then proceeds as described previously.
The main difference between this mode and the previous mode is that the host, not the TSC2005, decides when
the touch screen scan begins.
The time needed to convert both X and Y coordinates under host control (not including the time needed to send
the command over the SPI bus) is given by:
f
LPPRO
fOSC
OHDLY1
fOSC
OH1
fOSC
1
fOSC
OSC )OHCONV
fADC
@
)
)2 @ ǒ
Ǔ)2 @ N @ ǒB)2 @
(
)
Ǔ ǒ Ǔ ǒ Ǔ
ǒ
Ǔ
tCOORDINATE
+
tPVS)tPRE)tSNS
)
(7)
Programmed
for
Host-
Controlled
Mode
(PSM = 0)
CS
Deactivated
CS
Deactivated
CS
Deactivated
Programmed
Reading Reading
X-Data Y-Data
Register Register
for
X-Y
Scan Mode
tCOORDINATE
Waiting for Host to
Write Into
Control Byte 1 D[6:3]
Waiting for Host to
Write Into
Control Byte 1 D[6:3]
Sample, Conversion,
and Preprocessing for
X Coordinate
Sample, Conversion,
and Preprocessing for
Y Coordinate
Detecting
Touch
Detecting
Touch
Detecting
Touch
Detecting
Touch
PINTDAV Programmed:
Touch is Detected
As PENIRQ,
CFR2, D[15:14] = 10
Touch is Detected
As DAV,
CFR2, D[15:14] = 11 or 01
Touch is Still Here
As PENIRQ and DAV,
CFR2, D[15:14] = 00
Figure 33. Example of an X and Y Coordinate Touch Screen Scan using TSMode 2
34
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