
2. Working principle: J903 is a 3-in-1 card holder which can read SD/MS card. When machine
switches in card read state, after inserting a SD card into card holder, detect switch on card holder
closes, SDCD signal becomes low level, MT1389HD begins to read SD content and then send to Mt1389
through data line SDD0-SDD3 for decoding to revert AV signals. MS card working principle is the same
with that of SD card. J901/J902 is an USB port, ADG713 is an USB port switch. When machine is set in
USB1, USB_SWITCH outputs high level signal. When machine is set in USB2, USB_SWITCH outputs a
low level signal to control working state of U901 directly.
- 92 -