Hardworking Strawberry

(1)OSI - 3 layer
(2)Master-slave protocol , not event-driven
(3)Advantage: Flexibility capability

Transmission Mode:
(1) Remote Terminal Unit(RTU): binary 表示
(2) ASCII: 將RTU模式中4位數字結合起來以ASCII儲存

ASCII的優點是可以接受大於1秒的delay(RTU不行)，

但同樣的data在ASCII mode下整個message的長度會是RTU模式的2倍

Function code : 04 - read input register