Delta RMC101 User Manual download pdf (Page 475)

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101

PROFIBUS-DP 5.4

Communications 5-225

• Wait until the Read Request bit is equal to the Read Acknowledge bit. When they are equal, the

RMC will have updated the Read Data area with the requested data.

• Use the data in the Read Data area of the Response Block input registers. Make sure that you do

not change the Read Request bit until you are done with the data in the Read Data area.

To request a write to the RMC, use the following steps:

• Wait until the Write Request bit is equal to the Write Acknowledge bit. If they are not equal, the

RMC is currently processing a write request.

• Copy the values you wish to write to the RMC into the Write Data area of the Command Block

output registers.

• Set the Write Address and Write Length output registers. See RMC Register Map (PROFIBUS-

DP Message Mode) topic for a description of all RMC registers and their addresses.

• Toggle the Write Request bit.

• Wait until the Write Request bit is equal to the Write Acknowledge bit. When they are equal, the

RMC has received the data written to it.

The RMC processes reads and writes separately. That is, it is not necessary for a write to

complete before starting a read, and in fact, you can simultaneously request both a read and a

write; the write to the RMC will occur first, and the read from the RMC will occur after the write

has completed. When both are done, both acknowledge bits will be toggled simultaneously.

To further clarify the ordering, keep these basic rules in mind in Message Mode:

• Do change all write data, the write address, and the write length before toggling the Write

Request bit.

• Do change the read address and read length before toggling the Read Request bit.

• Do not change the Read Request bit after a read request until you have processed the data in the

Read Data area.

• Do not change the write data, the write address, or the write length when the Write Request bit in

the output synchronization register does not match the Write Acknowledge bit in the input

synchronization register.

• Do not change the read address or the read length when the Read Request bit in the output

synchronization register does not match the Read Acknowledge bit in the input synchronization

Using Splines with PROFIBUS

Wait bit 7 is used by the Profibus DP communications so the user can tell when spline downloads

are finished. The Profibus DP spline processing routine sets wait bit 7 when a download to the

spline area is detected. The user can then use the step table and the Check Wait Bits link to be

sure the spline is ready before executing the spline.

5.4.7.2 RMC Register Map (PROFIBUS-DP Message Mode)

Tip: The RMCWin Address Tool provides an easy way to identify addresses in the RMC. Simply open

the Address Tool and then move the cursor to any field in RMCWin that represents an RMC Register,

and the Address Tool will display the address in the address format of your choice. See Address Tool

for details.

The RMC module has 64K (65536) 16-bit registers that can be read from or written to over

Ethernet, Modbus Plus, and PROFIBUS-DP. Each register is assigned an address. However,

under the different communication methods, different addressing schemes are used. This topic

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