freeport communication

Hi there
can anyone answer me about freeport in s7-200??
does it send just standard ascii characters?
or is it like ppi (has some kind of secret)?
if i want to communicate with another rs485 device, should i use the freeport to just send ascii characters?
if i want to communicate with the pc, then should i use a standard r2485/232 converter?

and please don't tell me to buy the pc/ppi cable

thanks in advance :site:

freeport in PLC send data in 8bit(bytes)0...255.
ascii character depend on your PC when you receive the data from freeport in PLC. it can be "char" or "byte".you can use MScomm to receive this data.
if you don't want to buy PPI you can do a cable by yourself(use 75176 and Max232),i did a PPI for myself, it work very well.
freeport can connect PLC with many device(microcontroller,AVR...)

Thank you for your reply, i'm really releived :nodi:

I have another request if you don't mind, my project is to connect my s7-200 cpu to a microcontroller (PIC16f628). Obviously the PIC receives data in TTL voltage level. I already used the 75176 to change the RS485 voltage level to TTL an connected it to the port of my cpu. I wanted to out the result on a 7-segment dislpay.

This worked well when i connected my PIC to the PC serial port through MAX232, but when i use the 75176 with the CPU, the PIC shows weird data.

Any suggestions???

Please can you send me a schematic of your own made PPI??

In freeport mode you could send any 7 or 8-Bit character no matter if binary or ascii interpreted.

Check if you wired A and B properly. Refer chapter 7 at S7-200 sytem manual. Otherwise add RS485 termination and Pull Up/Down resistor (all in chapter 7).

You have to switch/enable some Pin on your reciever IC to select send or receive mode trough your PIC. Refer SN datasheet.
If this not helps out send something with S7-200 and check it with digit.scope or analyzer. Alternate try a MAX48x (e.g. 487).