In the MVI56-BAS how can I transfer a string to the CLX Processor?

There's no direct way to transfer a string to the ControlLogix processor from the basic module, but you can search for all the characters inside the string and send that to the ControlLogix processor. A very simple program to do that would be:

rem $(0) contains the string to send to the processor
push 0
call 68
pop l
rem the string length is extracted
push int(l)
push 201
call 25
rem the length is transferred to the processor
for i=1 to l step 2
rem all the ASCII chars are extracted
value = asc($(0),i) + asc($(0),i+1) * 256
push value
push int(i/2) + 202
cal l25
rem and transferred to the processor
next i
call 54
return