***  refer to demo10 for more information ***
1. there is a touch screen connect to SIEMEMS's S7 PLC
2. the S7 connect to 7188, 7188 connect to 4*7052+2*7043+1*7053
3. if the user press OUTPUT-ICON in touch screen
   --> the touch screen send message to S7
   --> S7 send this message to 7188
   --> 7188 converter this message to control 7043's D/O
4. if there is any D/I change state
   --> 7188 will find that some D/I is changed
   --> 7188 send message to S7
   --> S7 send message to touch screen
   --> touch screen show the differn STATE-ICON in screen
5. in this way, the 7188 can be used as a bridge between 7000 & S7
   --> S7 will receive message if the 7000's D/I is change
   --> 7000's D/O will change if S7 send control message out
   --> S7 can direct control 7000 series modules in this way
6. This way can be applied to any PLC