[ASAHI KASEI]
Interface for Touch Screen A/D Converter
A/D data for Touch Screen is controlled by 4-wire I/F, TADE, TADCK, TADRDY, and TADOUT.
The rising transition on TADE pin initiates a conversion cycle. Tracking and A/D conversion takes 16 TADCK with
TADE "H" state.
First 3 TADCK is for tracking time. At the falling edge of 4th TADCK, TADRDY goes "H", which shows that most
significant bit (MSB) is ready to output on TADOUT, and the AK4533 outputs MSB at the same time on TADOUT.
The AK4533 continues to output A/D data serially at the falling edge of TADCK. At the 15th falling edge of TADCK,
the AK4533 outputs least significant bit (LSB). TADOUT can be returned to "L" at the falling edge of 16th TADCK.
TADE must be set to "L" per completion of one A/D conversion cycle. TADE can be set to "L" at the same time of the
falling edge of 16th TADCK.
If 17 or more TADCK is input to the device, the output of TADOUT is "L".
Tracking
Conversion
TADE(i)
1
2
3
4
5
6
7
8 9 10 11 12 13 14 15 16
TADCK(i)
TADRDY(o)
TADOUT(o)
D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Figure 18. The Timing of Touch Screen A/D Converter
Measurement Sequence
Figure 19 shows the case in which TPX_TOP and TPY_BTM terminals are supplied by VA and AGND respectively,
and in which ADC measures the voltage on TPY_TOP pin. The write 0x00 to 07h register via A/T I/F activates this
configuration. A/D data should be read through TC I/F after the input voltages to touch screen are stable.
The value must NOT be written to 07h register while TADE is "H".
<Revision 0.9a>
31
July 00
AKM [ ASAHI KASEI MICROSYSTEMS ]
