Samsung S3C2451X User Manual page 643

S3C2451X RISC MICROPROCESSOR
FUNCTION DESCRIPTIONS
A/D Conversion Time
When the PCLK frequency is 50 MHz, the prescaler value is 49 and total 10-bit and 12-bit conversion time is
given:
A/D converter freq. = 50 MHz/(49+1) = 1 MHz
Conversion time = 1/(1MHz / (5cycles)) = 1/200 KHz = 5 us
This A/D converter is designed to operate at maximum 5 MHz clock, so the conversion rate can go up to
1MSPS.
Touch Screen Interface Modes (AIN6 ~ AIN9)
1. Normal conversion mode (AUTO_PST = 0, XY_PST = 0)
The operation of this mode is identical with AIN0~AIN5's. It can be initialized by setting the ADC Control
Register (ADCCON) and ADC touch screen control register (ADCTSC). All of the switches and pull-up
resister should be turned off (reset value 0x58 makes switches turn-off). The converted data can be read out
from ADC conversion data 0 register (ADCDAT0).
2. Separate X/Y position conversion mode (AUTO_PST = 0, XY_PST : contorl)
This mode consists of two states; one is X-position measurement state and the other is Y-position
measurement state.
X-position measurement state is operated as the following way; set XY_PST is '1' and read out the converted
data (X-position) from ADCDAT0. The end of X-position conversion can be notified by interrupt (INT_ADC).
Y-position measurement state is operated as the following way; set XY_PST is '2' and read out the converted
data (Y-position) from ADCDAT1. The end of Y-position conversion can be notified by interrupt (INT_ADC).
State
X-position measurement
Y-position measurement
3. Auto(Sequential) X/Y position conversion mode (AUTO_PST = 1, XY_PST = 0)
Auto (sequential) X/Y position conversion mode is operated as the following. Touch screen controller
sequentially converts X-position and Y-position that is touched. After touch screen controller converts X-
position data to ADCDAT0 and then converts Y-position data to ADCDAT1, Touch screen interface generates
interrupt (INT_ADC). The measurement states are automatically changed.
XP
VDDA_ADC
AIN9
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
ADC AND TOUCH SCREEN INTERFACE
NOTE:
XM
VSSA_ADC
Hi-z VDDA_ADC
YP YM
AIN7 Hi-z
VSSA_ADC
24-3