Acer AL1702 AL1702 Service Guide - Page 8

AL1702 3.5.3 X302 crystal The X302 crystal is 11.0592MHz, support the operated clock to the MCU. 3.5.4 Reset circuit The C396, R379, D316 is support reset signal to the MCU, then MCU have output hardware reset signal (HWRESET) to the scaler. 3.5.5 I308EEPROM The I308 is 24LC16 EEPROM, the data transfer between I308 and MCU is effected through the IIC bus SCL (pin14) and SDA (pin13) of MCU. The OSD related setting data, I305 control data and other service data, to be stored in I308. 3.5.6 P308 connector The P308 has support keypad function. Control is give effect to for the push switch to be used when the user changes the parameters, in order to modify the respective setting values. Whether the switch has been pressed is identified with the switch input level that is turned "L". Each switch input port is pulled up at outside of MCU. Related ports of I307 based on Table 1. Each parameter is stored in the I308 EEPROM, the contents of which are updated as required. The P308 have LEDGreen and Amber light, the LEDGreen signal pin 36 from I307 MCU, and the LED Amber signal pin 37 from I307 MCU. Table 1 Related ports of I307 Pin No. I/O Signal name Pin 3 I KEY_POWER Pin 2 I KEY_MENU Pin 41 I Pin 42 I Pin 1 I KEY_DOWN KEY_MINUS KEY_PLUS Function Soft power switch input Exit/Enter switch input ↓ switch input ← switch input → switch input Remarks Power key Enter / withdraw from OSD Down key - / Mute key + / Auto key 3.5.7 Audio control function The I307 MCU output signal control audio mute and power, the pin33 is mute signal, the pin32 is controlled audio power signal. 3.5.8 Scaler programmed function The I307 MCU is used DDR direct bus, between I305 MST8111B and MCU I307. 3.5.9 ISP and DDC2Bi function The DDC2Bi is VESA standard for the host PC system, it can through DDC2Bi bus control LCD monitor. The I309 will off DDC_CLK and DDC_DAT signal, when LCD monitor is no power. Can use ISP function for firmware modification. The pin29 is bus clock (DDC_CLK), the pin28 is bus data (DDC_DAT). It is same of the IIC data bus. 3.5.10 The power save sequence function First disable I307 pin31 (BKLT_EN) from H to L of LCD module back light power, delay some time, then disable I307 pin9 (PANELVCC_EN) from H to L of LCD module power, and disable I307 pin32 (AUDIO_EN) from H to L of audio power, and through 3-wire bus programmed I305 MST8111B to power down mode. Page 6