Basic understanding how to address I/O

[splash]

Hello guys,

its my first post on this forum. I am intermediate user but just started working with actual hardware PLC. i have s7-315 siemens CPU. and i have problem about addressing to I/O in my program.

Please explain me everything related to how to address that exact pin on input or output. For example i have DI 32 *DC card. And over it there are 40 screws or slots. i understood top 2 is for supplied voltage and bottom 2 is for ground. but how to address them when i want to use in my program S7.

while hardware in my s7 shows something different. its showing I 8....11. what does that mean. and what if i want to access first pin of this Input module.

damnnn

 

[JRW]

How about some screenshots of your hardware config...
Then we can explain "everything".

 

[ASF]

Short answer to get you started: Siemens PLC addressing works in bytes. A byte is 8 bits. So, your 32-channel input card has 4 bytes.

You can define what bytes to use for each card in the hardware configuration. If you configure that 32 bit input card to use bytes 0-3, then your addresses will be:

I0.0
I0.1
I0.2
...
...
I0.7
I1.1
I1.2
...
...
I1.7
I2.0
I2.1
...
...
I2.7
I3.0
I3.1
...
...
I3.7

You could equally configure them to be bytes 29-32, and then you would have I29.0 through I32.7. Completely up to you. Just make sure there's a logical pattern for ease of troubleshooting.

As JRW mentioned, some screenshots of your hardware configuration will make it easier for us to help

EDIT: just noticed your comment about hardware configuration showing 8-11. If you mean what I think you mean, then that means that the card has been configured to use input bytes 8 through 11. So your first 8 inputs are I8.0 through I8.7, and your last 8 inputs are I11.0 through I11.7.