Delta RMC151 - Manual (Page 424)

RMC70/150 and RMCTools User Manual
For serial (RS-232/485) and Ethernet communication, each axis has a Command Request
and Command Acknowledge bit.
• Command Request Bit (REQ)
To set the Command Request bit, add 256.0 to the command. For example, writing
20.0 to the Command register would issue the Move Absolute command with the
REQ bit cleared. Writing 276.0 to the Command register would issue the Move
Absolute command with the REQ bit set.
• Command Acknowledge Bit (ACK)
The Command Acknowledge bit is bit 31 of the Status Bits register. When a
command has been received by the RMC, it will update the ACK bit in the Status
Bits register to match the REQ bit of the command.
The ACK bits of all axes whose Command registers are written to in a single
transaction will be modified at the same time. This allows the user to take a
shortcut and, if they are writing to all axes every time they issue a command to
even a single axis, only check the ACK bit on axis 0 (compare examples 2 and 3
below).
The RMC keeps track of the REQ and ACK bits for each communication channel. The REQ
and ACK bits of one communication channel will not interfere with the REQ and ACK bits
of another channel. For example, if two PLCs are connected to an RMC75E via Ethernet,
each can independently use the REQ and ACK bits. Likewise, the REQ and ACK bits of a
PLC connected to the RMC75S serial port will not interfere with the REQ and ACK bits of
another PLC connected to the Monitor port.
Note:
This means that the Ack bit will NOT be visible in RMCTools, since it uses a different
communications channel!
The REQ and ACK bits will work correctly even if the Status Bits register is read via the
Indirect Data Map.
The ACK bit defaults to 0 when the RMC powers up. When starting up a PLC program, the
PLC can write zeros to all the Command registers, which will immediately set the ACK bit
for each axis to zero, giving them a known state.
Examples
The examples below refer to several RMC registers. Their addresses in each RMC are
given here for your convenience:
Register Name RMC70 Address RMC150 Address
Axis 0 Command register %MD25.0 %MD40.0
Axis 0 Command registers %MD25.0-9 %MD40.0-9
Axis 0 Status Bits register %MD8.0 %MD8.0
Axis 1 Command register %MD25.10 %MD40.10
Axis 1 Command registers %MD25.10-19 %MD40.10-19
Axis 1 Status Bits register %MD9.0 %MD9.0
Axis 0 ACK bit bit 31 in %MD8.0 bit 31 in %MD8.0
Axis 1 ACK bit bit 31 in %MD9.0 bit 31 in %MD9.0
Example 1: Commanding a Single Axis
1. On startup, the user writes 0.0 to the Axis 0 Command register, and clears an internal
coil in the PLC, which we'll call Axis0Req. Now the REQ and ACK bits are set to zero.
2. When it is time to write a new command, the user compares the Axis 0 ACK bit (bit 31
of the Axis 0 Status Bits register) with Axis0Req. If they are not equal, he will wait
404 Delta Computer Systems, Inc.