HUST H2N Connecting Manual
7 - 2
7.1.3 PLC and PLC Editor Graphical Symbols
The basic graphical symbols used in PLC and the PLC Editor are coil, contact, timer,
counter, and register. For the details of these symbols, please refer to HUST PLC
Operation Manual.
7.2 Composition and Modification of A Ladder Diagram
Writing a ladder program is a tedious work. To avoid or lessen the potential
problems when writing a ladder program, HUST suggests a flow chart (See Fig 7.1)
to follow as below:
Step 1: Print the Ladder Diagram
(User can skip this step if writing a new ladder diagram.)
Print out the old ladder diagram (HUST H2N Standard ladder) from print command
(PRN) in PLC Editor. User is encouraged to study this old ladder diagram carefully
before making any revisions. It is also helpful if the user fully understand the I/O
connecting structures for HUST H2N controller. If necessary, please review Chapters
4~6 again.
Step 2: Define Your I-bits, O-bits and the Timing Chart
To control machine tool's motion, the user should fully understand the relationships
between the machine tool and the HUST H2N Series I/O interface. At this point, the
user must define the I-bits and O-bits to be used, according to the I/O interface
connection. In addition, the user should know the exact I/O timing so that the
mechanical actions can flow flawlessly in a sequential manners.
Step 3: Use of PLC Editor to Edit Ladder Diagram
When the I/O interface has been assigned and the timing decided, the user can use
the PLC Editor to edit, compile and print the ladder diagram for the new model.
Once the new model has been completed, user can use the "Ladder Simulation"
function to test the revised ladder directly from the PC through RS232C interface.
Make sure the new program does not exceed 24-k bytes of memory.
Step 4: Translation of Ladder Diagram to 68000 Machine Code
When the new ladder diagram has been completed, it can be translated to 68000
machine code by using COMPILE command in the HUST PLC Editor. The compiled
program will have four (4) different files, appending to user's directory. The one with
"*.tsk" is for EPROM or FLASH-ROM writing.
Step 5: Writing and Installing the EPROM / FLASH-ROM
When the jobs in Step 4 have been done, user can use an EPROM writer to write the
file "*.tsk" onto EPROM 27C010 or FLASH-ROM 29C010 for HUST controller.
The details of EPROM or FLASH-ROM writing will be discussed in Chapter 8.
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