Please point out how to write a method for sending data to a PLC in VB, preferably with an example

It seems to have something to do with the agreement.

It's relatively simple, database + interface, the key is the design of the database.

Let's take a look at FX's communication protocol first.

For example, if you write 1234 to the two memories starting with D123, ABCD then select Hexadecimal, Input in the serial debugging tool.

02h 31h 31h, 30h, 46h, 36h 30h, 34h 33h, 34h, 31h, 32h, 43h, 44h, 41h, 42h 03h 34h, 39h point sending.

If the ACK (06H) is received, it is accepted correctly.

Received nak (15h) acceptance error.

Take a good look at the protocol.

Figure out the instructions, read the manual.

ld starts counting.

The LD counter resets when it is complete.

CTU C1, 5 counter output after 5 counters.

LD is 1 on the first scan

movr 16 0, md0 md0 zero.

LD C1EU Rising Edge.

r 16 1, md0 md0 plus 1

ldr= md0, 16 03 equals 3 times.

Output y1

You can start with a trapezoidal diagram and then display it as ST, which can be done with the S7-300 from Siemens.

You can use other configuration software, such as Configurator. It is also possible to write a program in VB, read data from PLC, and write it to the database. If you don't need a surveillance footage, I think VB is better.

PC needs to install OPC server and then simply write a program with VB to read the data captured by OPC and write it to the database, and the more mature OPC server will provide VB and VC program examples for your reference.

It's similar to the pascal language.

For example, a start-up and stop-stop ladder is shown as ld startor lamp

ani stop

out lamp

In terms of ST (structured text), it is:

lamp:=(start or lamp) and not(lamp);

Structured text is one of the more popular programming methods in the new PLC. Similar to the C language, the acacia has if, then; while, else, and other commands.

Hello, what plc program do you want to read? What exactly does it do?

Ask for help ......I'll give you a "help"!

Recommended reading "The Wisdom of Questioning".

The hardware is generally serial port communication, VB open a serial port, know the protocol of the PLC programming port, just send it according to the corresponding format, each manufacturer is not the same, if the port with 485, support the modbus protocol, it is better, the specific IR area is a maintenance type or an input type of test on the line, the function code is nothing more than 03 or 04