User manual

Transferring Data Using Communication Blocks
132
33002479 06 07/2008
Function Mode of
the CREAD_REG
Block
Although a large number of CREAD_REG function blocks can be programmed, only
sixteen read operations may be active at the same time. In such a case it is
insignificant whether they are the result of this function block or others (for example,
MBP_MSTR, MSTR, READ_REG). All function blocks use one data transaction
path and require multiple cycles to complete a job.
The entire routing information is contained in data structure WordArr5 of input
AddrFld. The type of function block connected to this input and thus the contents of
the data structure depends on the network used.
Please use:
z TCP/IP Ethernet: the function block TCP_IP_ADDR
Note: A TCP/IP communication between a Quantum PLC (NOE 771 ••) and a
Momentum PLC (all TCP/IP CPUs and all TCP/IP I/O modules) is only possible,
when only one read or write job is carried out in every cycle. If several jobs are sent
per PLC cycle, the communication stops without generating an error message in
the status register of the function block.
Note: A TCP/IP communication between a Quantum PLC (NOE 211 00) and a
Momentum PLC (all TCP/IP CPUs and all TCP/IP I/O modules) is only possible,
when only one read or write job is carried out in every cycle. If several jobs are sent
per PLC cycle, the communication stops without generating an error message in
the status register of the function block.
Note: For experts: The WordArr5 data structure can be used with constants as
well.
Note: This function block puts a heavy load on the network; therefore the network
load must be carefully monitored. If the network load is too high, the program logic
should be reorganized in order to work with the READ_REG function block, a
variation of this function block that does not operate in a continuous mode, but
under command control.