Delta RMC151 - Manual (Page 303)

5 Programming
With Modbus/RTU or Modbus/TCP Addresses:
From the RMC150 Register Map - File 40 Commands, we see that the
addresses for the Axis 0 command registers start at register offset 20481. The
offsets must be prefixed with a 4. To issue this command to the RMC70 via
Modbus/RTU or Modbus/TCP, the user programs the PLC to do the following:
d. Write 90 to 420481
e. Write 0 to 420483
f. Write 8 to 420485
Command Format
Each RMC command consists of a command number and command parameters.
• Command Number
Each RMC command has a number associated with it. You must use this
number when you issue a command to the RMC. The number is typically
included in parentheses whenever the command is mentioned. For example,
the Move Absolute Command (20) has a number of 20.
• Command Parameters
Some commands have command parameters. For example, the Move
Absolute Command (20) has 5 command parameters: Position, Velocity,
Accel rate, Decel Rate, and Direction. When you issue a command, you must
include any command parameters.
Notice that the Command Number and Command Parameters are all floating
point numbers, as seen from the PLC or HMI issuing the command. However,
the command number must be a whole number (e.g. 20, or 20.0, not 20.1)),
and certain command parameters must be integers or are limited to a certain
range, depending on the command.
For more details on commands, see the Commands Overview topic.
Advanced Details
Immediate Commands
Certain commands in the RMC are immediate commands. There is no limit to the
number of immediate commands that can be issued to an axis per loop time,
whereas a maximum of one non-immediate command per loop time can be
issued to each axis.
Immediate commands are usually not motion commands. The ability to issue
multiple immediate commands in one loop time affects primarily the user
programs, since it is difficult to issue many simultaneous commands via the
external communications.
Commands Issued Simultaneously
Commands sent simultaneously to the RMC in the same communication block
will always be issued simultaneously. For all communications methods, the RMC
waits until the entire communication block is received before issuing any of the
commands in the block. The commands received in this block are referred to as
a command set. Such a command set can contain at most one command per
axis, with the exception of immediate commands in user programs, which are
unlimited.
Command Queue
As command sets are received from various sources, they are placed in a
command queue. Each control loop, the controller processes command sets from
the queue on a first-in first-out basis, stopping when it reaches a command set
that would issue a non-immediate command to an axis that has already
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