2.2 The IBM 7171 ASCII Device Attachment Control Unit - Index of

2.5 Customizing the IBM 7171The IBM 7171 is ready to operate, provided its configuration fits the requirementsof the user's installation. The following types of customization changes can bemade:1. Changing Communication Lines - For each IBM 7171 port address the linespeed (or autobaud detection), parity selection, number of stop bits, terminaltype, valid types list, and other parameters are predefined but may be changed.For a complete definition and the default settings as delivered, refer to section4.4.2, "Ports Area Layout" on page 4-21. The procedure for changing thesepredefined parameters for each communication line is explained inChapter 4, "Customizing IBM 7171 Tables."2. Generating Terminal Definition Tables - Existing tables can be modified (customized)and new ones created for new terminal types. Detailed informationon how to do this is contained in Chapter 4, "Customizing IBM 7171Tables."2.6 Operating Environment of the IBM 7171The IBM 7171 requires the following system configuration and programmingsupport:2.6.1 System ConfigurationHost Processor: The IBM 7171 will support IBM 43xx, 308x, or 3090 processorsrunning VM/SP Release 3 or MVS Release 3.8. The IBM 7171 must be attachedto the host via a block multiplexer (BMPX) channel. Several IBM 7171 's can beattached to a single BMPX channel at the same time. However, this could affectthe performance of the IBM 7171 depending on what other I/O devices areattached to the same channel. It is recommended that the IBM 7171 not be put onthe same channel as tape drives for performance reasons.Up to 64 ASCII devices may be attached to a single IBM 7171. When more than32 devices are attached, the IBM 7171 appears as two 3274-1D control units.2.6.2 ASCII Display Terminal RequirementsTo be attached to the IBM 7171, ASCII display terminals must meet the followingminimum functional requirements. The ASCII display terminal must be capable offull duplex character mode operation, must be connected point to point, must usethe Start/Stop control protocol, and must use 7 bit ASCII code. The terminal mustperform the following functions upon receiving an appropriate character sequencefrom the control unit:• Clear screen or clear to end-of-screen.• Absolute cursor positioning.• A character written to the screen should replace, not overstrike, the previouscharacter in that position. APL mode is an exception, when overstrike charactersmust be formed.Chapter 2. System Description and Operation 2-11