User`s guide

Page 26

Controlinc 1746-C (Version 5.21) Network Master Users Guide (2004-11-18)

4.3.1. Operation: PLC (Write Data Tables To) or (Read Tables From) the

1746-C

Relative to M0/M1 transfers, from the 1746-C perspective, there is no difference in handling

• Writing a value to any table in the 1746-C memory.

• Writing a value to a table in the 1746-C memory that is also passed on to the specified actuator

on the network.

They both require a M0 file transfer command. The only difference is in the 2

word in the block being

transferred (word [1]).

• If word [1] == 0, then this M0 transfer is a command to read a table from the 1746-C.

• If word [1] =/= 0, then this M0 transfer is a command to write data to a table in the 1746-C.

To perform a transfer of table data:

1. The PLC interface time-slice has now started.

2. The 1746-C looks to see if a new M0 file has arrived from the PLC. If not, this operation

terminates and must be restarted on the next PLC interface time slice. Otherwise, continue.

3. Since a new M0 file is here, the 1746-C copies the table into its own memory.

4. If word [3] indicates an ESD command sequence (start or stop the ESD condition) then that is

outputted to the entire network of actuators on both ports.

5. If word [1] == 0, then a read-only request command was made and the appropriate table is

copied into the M1 exchange buffer.

If word [1] =/= 0, then this was a write command and this table is copied into 1746-C memory.

A final “resultant” table (what will be stored in the 1746-C and potentially sent out onto the

network) is then copied into the exchange buffer to be fed back to the PLC.

6. The new M1 file is prepared to be transferred to the PLC such that if the received M0 file

indicated

• A read command – the data the PLC requested in a read table command.

• A write command – the immediate feedback of the command structure the 1746-C is

about to execute.

7. The 1746-C looks to see if the last M1 file was already read.

8. The new M1 file is transferred after the PLC indicates that the previous M1 file was read or the

1746-C system times waiting for the previous M1 to be read. Note that if the 1746-C times out

waiting, the previous M1 file will be overwritten.

9. After the M1 file is sent, if the command was to write data to the actuators, the 1746-C will now

loop through and write to all “appropriate” actuators on the network.

10. The PLC interface time-slice is now finished.