RTD2523 datasheet(21/129 Pages) ETC2

21 / 129 page

Realtek

RTD2523/2513

4.9 The Programmable Schmitt Trigger of HSYNC

To get better waveform of the input HSYNC, we have a programmable Schmitt Trigger circuit.

For different HSYNC amplitude and polarity, we can select different setting of the threshold voltage.

The Vt

+ and the V

- can be selected by register 0xED.

We can select the old mode or the new mode. When using the new mode we can directly

determine the positive threshold voltage (1.4V, 1.6V… 2.6V), and we can choose the distance from

the Vt

+ to determine the V

- (0.6V, 0.8V, 1.0V, 1.2V). We also can finely tune the voltage by minus

0.1V. For application, we can select different threshold voltage by the polarity of the HSYNC. The

control register is 0xED.

Figure 18 The Schmitt Trigger Behavior Diagram

4.10 Crystal Frequency Output

RTD can output crystal frequency or half crystal frequency to external MCU to save a crystal

device. After power on, RTD latch the state of PLL_TEST2 pin to determine which frequency to

output, and the result shows in TCON register address 0x00[0]. 0 is for half of crystal frequency and

1 is for crystal frequency. When power on, crystal frequency output to TCON12 and TCON13.

Hence, crystal-in pin of external MCU can connect to TCON12 or TCON13. Firmware can turn off

the signal output of other pin, and the control register is in TCON register 0x00[1] and 0x00[2].

4.11 Pin Out Configuration

RTD supports TTL, LVDS and RSDS output interface. After power on, display port is high

impedance. Firmware can set its control register in TCON address 0x03[7:6] to select output

interface. Refer to Pin Out Diagram for output pin definition.

RSDS interface

Input HSYNC

Output HSYNC

RTD2523 датащи(PDF) 21 Page - List of Unclassifed Manufacturers