User`s guide

DC 900-1340I 33

Chapter

BSC Protocol Summary

2.1 BSC 3270 Protocol Implementation

The Protogate Binary Synchronous Communications (BSC) product is a software pack-

age that allows applications running on the client to communicate through one or more

serial ports (links) to devices using the IBM BSC 3270 and/or the BSC 2780/3780 pro-

tocol.

Each BSC serial link handles all low-level protocol activity thus freeing the client pro-

cessor to perform other tasks. User-written client application programs interface to the

BSC software through the Freeway DLI functions, described in Chapter 3 and

Chapter 5.

Each BSC serial link can be configured as a 2780/3780 link, a 3270 control station (sim-

ilar to an IBM 3705 communications controller) or a 3270 tributary station (similar to

an IBM 3274 cluster controller). Each link operates independently of other links on the

same server and can be configured with different communication options.

IBM 3270 BSC is a half-duplex, multipoint protocol used by the IBM 3270 data display

system. Details of the 3270 protocol can be found in the documents GA27-3004, Gen-

eral Information — Binary Synchronous Communications, IBM, and GA23-0061, 3274

Control Unit Description and Programmer’s Guide, IBM. The Protogate version of the

IBM BSC 3270 protocol follows the rules set forth in the above documents, and its

implementation is described throughout this manual.