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AChannel Command setup to issue a single send can have only one pendingsend transfer.
indication will be placed in the COMMREQ Status word. If the channel number is the same as a channel already in use, the channel will be
(Word 9) Number of Send Repetitions: Word 9 specifies the number of transfers to be performed before automatically completing the communications request and closing the channel. If this value is set to 1, only a single transfer will be issued. If this value is set to 0, transfers will be issued on the requested period until the channel is aborted.
(Word 10) Time Units for Send Period: Words
(Word 11) Number of Time Units for Send Period: Word 11 specifies the number of time units for the send period. The send period is in effect even when the Channel Command is setup to issue a single send.
Example Send Period Calculation: If Word 10 contains a value of 3 specifying seconds as the time unit and Word 11 contains a value of 20, then the send period is 20 seconds.
A send will normally be issued at the start of each send period. If the pending transfer has not completed during the send period, the Channel Error bit and Detailed Channel Status words will be set to indicate a
If the Number of Time Units is zero, a subsequent transfer will be issued as soon as the previous transfer completes; no period errors are reported by the Channel Error bit.
(Word 12) Timeout for Each Send: Word 12 specifies the time (in hundredths of a second) the Ethernet Interface will wait for a send transfer to complete before setting the Channel Error bit and Detailed Channel Status bits to indicate a
For most applications a timeout need not be specified because the send period, in effect, acts as a timeout. (Word 12 should be zero for no timeout.) However, there are two special circumstances in which specifying a timeout is recommended:
When the number of time units (word 11) is zero, so that a subsequent transfer will be issued as soon as the previous transfer completes and no period errors are reported. In this case a timeout value can be specified so that timeout errors will be reported by the Channel Error bit.
When the send period is very long (minutes or hours). In this case a shorter timeout value can be specified so the application doesn't have to wait for the send period to expire before taking action.
(Word 13) Local PLC - Memory Type: Words
(Word 14) Local PLC - Memory Starting Address: Word 14 specifies the starting address in the local PLC from which the data is to be sent
Chapter 4 Programming Communications Requests |