Rockwell Automation GMLC Reference Manual - Manual (Page 430)

Publication GMLC-5.2 - November 1999
DH-485 Value 393
The maximum number of contiguous remote elements which may be sent
using a single DH-485 Value block depends on the file type selected for
the element in question. See DH-485 Message Details for the limits for
each file type.
Wait for Message Complete
When you select Wait for Message Complete, one of the following
occurs:
• the program pauses until the requested value is received and no DH-
485 faults exist (in a Read type block)
• the remote device acknowledges receipt of the value (or values) and
no DH-485 faults exist (in a Send type block)
When the requested value (read type) or acknowledgment (send type) is
received, the program continues with the next block. If other tasks are
executing (multitasking), the task that contains this block pauses but the
other tasks continue to execute. A Wait for Message Complete selection
in one task does not halt execution of any other tasks or hang the task
dispatcher.
If you do not select Wait for Message Complete, the DH485 Value block
just requests (read type) or sends (send type) the specified value or values
and the program continues with the next block.
DH-485 Message Details
The DH-485 Value block, with Send Type selected, issues a Protected
Typed Logical Write with Three Address Fields command on the DH-485
network. Similarly, the Read type block issues a Protected Typed Logical
Read with Three Address Fields command on the DH-485 network.
Depending on the type and number of elements specified, up to 240 bytes
of data may be included in the command packet. The number of data
bytes in the command packet for each file type and the corresponding
maximum number of elements, which may be specified in the Multiple
Elements field, is shown in the following table.