SLC5/03 Input Buffer Chan 0

Big John T

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Nov 2006
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Is there anyway to see what is in the input buffer of chan 0 on a SLC5/03 from RSLogix? I'm sending an ASCII command out and the servo responds by executing the sequence called. The ACB returns 3 but neither the ARD or ARL put anything into the string file...

The servo responds with "ok" after the command is read by the servo. For some reason I can't read the "ok" in the slick...

John
 
This is the code I'm using

Ascii123.jpg



Sorry about the quality of the screen shot...
John
 
Last edited:
John,

after you send your string to the servo, clear the buffer, then compare your 'known' acknowledgement string with the buffer

What is the expected string you should be getting from your servo?

I will post what I'm talking about when I can find it
 
is this the same program you were working on last week or so? in the pdf that I posted you should be able to see what we did

the string we were looking for as a return was d2/d2
 
Big John T said:
Sorry about the quality of the screen shot...
Click to expand...

It must be nerves...shaking



Look at this,

1st read, then compare, then clear

Like I said we were looking for d2/d2, not sure how 'ok' would come across, is it a text they are returning, it has to be a ascii/hex correct? I'm still learning this also

asc1111.gif
 
John,

This is the ascii code...I think (anyone else can jump in and help) you would need to see this converted, ascii is hi/lows on a signal, so you would see numbers, are you getting anything back from the servo? where's Bernie when you need him :D
 
I'm nowhere near a unit to test this but, if I remember my only application which used the serial port to read characters, I had to use a test for the presence of the line before reading it. I used either ABL or ACB to look at the buffer. When it had what I was looking for (note - possibly 3 characters "o" "k" and a carriage return - check that out in your documentation) then I invoked the ARD (or it was possibly ARL).My application was complicated by a varying line length. I had to use the test instruction to check the line (which ended in consistent terminating character - note your port ASCII setup) then I moved the actual numer of characters to read into the Control structure for the read instruction.
 
I think you need to put a number other than 0 in your string length field. Just guessing, though. My initial feeling is that the value should be the number of characters from the ACB instruction.

In a branch above the ARD, insert a MOV with source A of R15:3.LEN and a destination of R15:4.LEN. Or for the short term just set R15:4.LEN to 3 and see what happens.

My guess is that if the instruction can't read the 82 characters that the length of 0 would ask for it will just wait until it can and never complete.

Keith
 

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