Rockwell Automation 1771-DB BASIC MODULE - Manual (Page 208)

Chapter
Call Routines 0–68 12
12 -18
Undefined. If you execute an undefined call, you receive the error
message, “
ERROR–UNSUPPORTED CALL .”
Use CALL 29 in conjunction with CALL 122 (page 13 -58) or CALL 123
(page 13 -66) to communicate between remote PLC processors and the
BASIC module internal string without local PLC processor interaction.
You can also use CALL 29, in conjunction with CALL 49 (page 12 -44) or
CALL 50 (page 12 -50), to communicate between remote SLC processors
and the BASIC module internal string (see String Data Types, page 8 -2)
without local PLC processor interaction. You must execute CALL 49, 50,
122, or 123 within the BASIC program before CALL 29.
CALL 29 is active when the internal string is the only choice in CALLs 49,
50, 122, or 123. In this situation, it is not practical to use the PLC block
transfer words to begin the transfer and to pass the status. The PLC
processor does not need to be involved. If you choose a PLC BTR or
BTW information, the local PLC processor controls the transfer with the
I/O bits. In this instance, when you attempt CALL 29, you receive a status
of 255.
When you execute CALL 29, the transfer is attempted. If you have not
executed the selected call (49, 50, 122, or 123) before executing CALL 29
you receive a status of 1 in the output argument. When you execute CALL
29 successfully, the value in the first character of the string (transaction
number) increments to designate that the transfer occurred. The range of
this character is 0–255.
Unlike CALLs 49, 50, 122, and 123, CALL 29 does not require PLC bit
handshaking at the end of the command when using an SLC file as a
source or destination.
Input and Output Arguments
This routine has one input and one output argument. The input argument is
the call you want to activate (CALL 49, 50, 122, or 123). The output
argument is the status of the transaction:
0 = successful completion
1 = chosen call (49, 50, 122, or 123) is not active
51 = PLC/SLC command already in progress
57 = bad input argument
255 = PLC BTW or BTR is chosen for CALL 49, 50, 122, or 123 and
CALL 29 is ignored
all other codes are identical to CALL 90/92 (see page 13 -18 or 13 -26)
CALL 28
CALL 29: Read/Write to a
PLC/SLC Processor from
the BASIC Module Internal
String