7 Ladder Diagram
7 - 1
7 LADDER DIAGRAM and EPROM
This chapter briefly explains the PLC ladder programs that come as a standard
equipment. Users who desire to change the sequential control of the HUST standard
PLC Ladder must fully understand the specific purpose of all the S-bits and C-bits that
are described in Chap 6 before attempting to make any change. Prior to making any
change, lay out and design all the I/O points that are required for the purposes. Note that
the S-bits, C-bits, and some I-bits are already defined in HUST H2N controller. Their
applications should not be altered or redefined. Otherwise, significant error may result.
7.1 Introduction to Ladder Diagram (PLC or Ladder Program)
A ladder diagram is a sequential control chart for the CNC controller, which in turn
issues a voltage command to do some mechanical actions. To edit or revise a PLC
program, an optional software called HUST PLC Editor can be used.
Before you start writing a PLC program, a chart depicting the mechanical actions
should be laid out, including the inputs and the outputs. Based on this chart, you can
start writing your PLC program. When the desired PLC program is completed, you
can use the function in the HUST PLC Editor to translate the PLC program to 68000
machine code (*.tsk file). You split this file into *.ODD and *.EVN files and burn it
into two blank EPROM as EVEN and ODD and replace the old ones on the CPU
main board. More on Eprom in Chap 8.
Following sections will be devoted to discuss the ladder diagrams provided in HUST
H2N standard PLC. For PLC Editor, please refer to HUST PLC Operation Manual.
7.1.1 Interface Signal Definitions for PLC Ladder Diagram (see Chap 6)
I-bit : Input signals to the PLC from external I/O devices.
O-bit : Output signals from PLC to external I/O devices.
C-bit : Command signals from PLC to CNC for motion control.
S-bit : CNC status signals to PLC for sequential control.
A-bit : Internal signals used by PLC itself for auxiliary purpose.
Register : R000~R099 for user application and R100~R255 for HUST system data.
R000~R199 whose data will be saved when power-off if MCM #86=256
and will not be saved if MCM #86=0.
7.1.2 Maximum Input/Output Points for PLC and PLC Editor
I-bit : 24 input points for PNP type and 144 points for NPN type board.
O-bit : 16 output points for external connections, 256 bits for PLC ladder Editing.
C-bit : 256 bits for HUST H2N PLC and PLC Editing.
S-bit : 256 bits for HUST H2N PLC and PLC Editing.
A-bit : 1024 bits for HUST H2N PLC and PLC Editing.
Timer : 256 timers available with time base of 50 ms, 0.1 sec, 1 sec.
Counter : 256 counters available for count-up, count-down, set, ring-up, ring-down .
Register : 256 registers available.
To Next Page
Loading...
Need help?
General
