17
7. Programming
One of the most popular and basic programming language is “ladder” (LD), however SFC or FBD is
becoming very popular. In this chapter, LD is introduced for easy understanding.
The simplest LD circuit consists of one contact and one coil as below.
In this picture, while the switch is ON, the light is ON.
This LD circuit is almost the same meaning as the above picture. The “contact” is condition for the coil
to be ON, and the “coil” is the result.
Basically input “X” is used for the contact, and output “Y” is used for the coil. The internal I/Os “R”, “M”
can be used for both cases depending on your program. (Y can work as a contact.)
Hitachi PLC handles the following I/O types.
A contact
(Normally open)
Normal coil
B contact
(Normally close)
Set / Reset coil
(MCS / MCR coil available)
Edge detection
(Low è High)
Timer (Other timers ; SS, MS, TMR,
WDT available)
Edge detection
(High è Low)
Counter (Other counters ; RCU, CTU,
CTD, CL available)
NOT
X0 Y100
X0
Y100
X0
Y100
X0 Y100
(=Input) (=Output)
Switch Light
TD
CU
To Next Page
Loading...
Need help?
General
