User's Manual

ADC AND TOUCH SCREEN INTERFACE S3C2450X RISC MICROPROCESSOR
24-4
4. Waiting for interrupt mode (ADCTSC = 0xd3)
Touch screen controller generates interrupt (INT_TC) signal when the stylus is down. The value of ADC touch
screen control register (ADCTSC) is ‘0xd3’; PULL_UP is ‘0’, XP_SEN is ‘1’, XM_SEN is ‘0’, YP_SEN is ‘1’ and
YM_SEN is ‘1’. Touch interrupt can be generated when stylus pen is down or up.
After touch screen controller generates interrupt signal (INT_TC), waiting for interrupt mode must be cleared.
(XY_PST sets to the No operation Mode)
Mode XP XM YP YM
Waiting for Interrupt Mode VDDA_ADC(Pull-up enable) Hi-z Hi-z VSSA_ADC
2.2.3 Standby Mode
Standby mode is activated when ADCCON [2] is set to '1'. In this mode, A/D conversion operation is halted and
ADCDAT0, ADCDAT1 register contains the previous converted data.
2.2.4 Programming Notes
1. The A/D converted data can be accessed by means of interrupt or polling method. With interrupt method,
the overall conversion time - from A/D converter start to converted data read - may be delayed because of
the return time of interrupt service routine and data access time. With polling method, by checking the
ADCCON[15] - end of conversion flag-bit, the read time from ADCDAT register can be determined.
2. A/D conversion can be activated in different way: After ADCCON[1] - A/D conversion start-by-read
mode-is set to 1, A/D conversion starts simultaneously whenever converted data is read.
Stylus Down
X-Conversion Y-Conversion
Stylus Up
AB C
= x (1/X-tal clock) or x (1/EXTCLK clock)
= x (1/PCLK clock) + 5 x (1/PCLK clock) x (PRSCVL+1)
= x (1/PCLK clock) + 5 x (1/PCLK clock) x (PRSCVL+1)
= Delay value of ADCDLY register
XP
YP
Figure 24-2. Timing Diagram in Auto (Sequential) X/Y Position Conversion Mode