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EPSON
S1C88409 TECHNICAL MANUAL
CHAPTER 5: PERIPHERAL CIRCUITS AND OPERATION (Touch Panel Controller)
5.17 Touch Panel Controller
5.17.1 Configuration of
touch panel controller
The S1C88409 has a built-in touch panel controller.
It can reduce external devices and load software
for designing systems. This touch panel controller
also features a capacity to resist noise.
The touch panel controller detects the coordinates
on a touch panel using two channels of the 10-bit
A/D converter.
Figure 5.17.1.1 shows the block diagram of the
touch panel controller.
5.17.2 Terminal configuration
The following signals are used to control a touch
panel.
BXH, BXL
These signals control the supply
voltage to the electrodes for detecting
X coordinates. BXH is the positive
electrode control signal and BXL is the
negative electrode control signal.
BYH, BYL
These signals control the supply
voltage to the electrodes for detecting
Y coordinates. BYH is the positive
electrode control signal and BYL is the
negative electrode control signal.
The output terminals for the signals are shared
with the I/O port terminals and they can be set for
controlling a touch panel by selecting the mask
option.
Table 5.17.2.1 Touch panel control signal output
terminals
Output signal
BYH
BYL
BXH
BXL
I/O port
P20
P21
P22
P23
The following two options are available:
1) Touch panel is used (The P20 to P23 terminals
are set as the touch panel control signal output
terminals.)
2) Touch panel is not used (The P20 to P23
terminals are set as the I/O port terminals.)
Note: When the touch panel function is selected
by mask option, the P20–P23 terminals are
configured as follows at initial reset:
P20 (BYH)
High level
P21 (BYL)
Low level
P22 (BXH)
High level
P23 (BXL)
Low level
The P20–P23 terminals are disconnected
from the I/O control and data registers, and
are controlled from the touch panel control-
ler. Thus it is unnecessary to configure
these terminals by software. The I/O control
and data registers for these ports can be
used as general-purpose registers.
Two channels of the A/D converter that is built
into the S1C88409 are used to input coordinates
from a touch panel. Two analog signal input
terminals can be selected from among the I/O port
terminals P30–P35 by mask option.
A/D
converter
Primary
average circuit
Noise
judgment circuit
Pen-up
decision circuit
A/D converter
control circuit
Panel
control circuit
Secondary
average circuit
Bus I/F
Drawing speed
judgment circuit
Average
control circuit
Interrupt
control circuit
Ch0 input
Ch1 input
AVDD
AVREF
AGND
AVSS
BXH
BXL
BYH
BYL
Interrupt request
Internal
data bus
Fig. 5.17.1.1 Block diagram of touch panel controller