SLU P message protocols

Multiple transmissions for one message are required if the workstation's transmission buffer is not large enough to hold all of the data to be sent. Multiple transmissions can also be used if the workstation user wants to segment the data. Multiple transmissions are logically related through the concept of chained messages. Each transmission of a multiple transmission message is identified by its position in the chain—that is, first-in-chain, middle-in-chain, last-in-chain as shown in the figure in Output messages.

In a SLU P system using chained input messages, the chaining indicator is used to specify the chain position of the transmission; it should not be set for an unchained message. The chaining indicator must be turned on for the first-in-chain transmission, turned off for each middle-in-chain transmission, and turned on again for the last-in-chain transmission.

When MFS is defined, input messages can be processed by the MFS. For input formatting, MFS does not distinguish between possible input components but assumes that all input comes from the 4701/4702 application program.