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Asynchronous Serial Communications Programmer's Reference Manual: HP 3000 MPE/iX Computer Systems > Chapter 1 Introduction
ASC Software Overview |
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The Asynchronous Serial Communications software provides the interface between the IEEE 802.3 LAN and the MPE/iX system. The software is included with the MPE/iX Fundamental Operating System (FOS). MPE/iX system software mirrors its related hardware in the sense that it is structured in modules, with each module handling the control of a specific type of hardware device. These modules, or managers, know which devices of their type are configured, or currently connected through a DTC connection, and handle all functions related to those devices. They manage terminal and printer I/O and are responsible for detecting errors that take place during communications and reporting them to the MPE/iX system. On LANs that do not include an OpenView Workstation, the ASC managers also manage the downloading and uploading of information for the DTCs configured on the system. The ASC managers define the characteristics of the devices they control. They determine, among other things, the type of communications protocol being used. The way in which the ASC software expects devices to act is defined in part at configuration time, but can be altered programmatically through use of the system intrinsics described in this manual. The ASC managers provide the interface between asynchronous devices and the File System. The File System is the part of the MPE/iX operating system that manages information being transferred or stored with peripheral devices. More information on the File System and how intrinsics are used to control devices can be found in Chapter 2 “Controlling Asynchronous Devices Programmatically” The MPE/iX system keeps track of all devices connected to it by means of configuration files. The network configuration information necessary to initialize and control the Datacommunications and Terminal Subsystem (DTS) resides in the NMCONFIG.PUB.SYS configuration file. This file is created through use of the Node Management Configuration Manager (NMMGR) utility. NMMGR is described in Using the Node Management Services (NMS) Utilities, while Configuring Systems for Terminals, Printers, and Other Serial Devices provides a detailed discussion of the configuration process. Effective with version A.30.00 of MPE/iX, HP 3000 Series 900 and HP 9000 Series 800 computers may be part of a network managed by the OpenView DTC Manager. Devices connected to the DTCs on such a network are configured through a PC-based network management workstation which is also attached to the LAN, and the DTC control software is subsequently downloaded from the PC. The connection between each host computer and the LAN is configured using NMMGR, along with profiles of the asynchronous device types that will be accepted for connection to the host, and the ldev numbers of devices that require a permanently associated (nailed) connection. However, many of the other parameters usually associated with a connection between a host system and each individual asynchronous device no longer need to be configured through NMMGR. Asynchronous devices attached to DTCs managed by an OpenView workstation can be configured as either nailed or non-nailed devices on the MPE/iX host systems to which they have access. A nailed device is one that is permanently associated with an ldev number through the NMMGR configuration of an MPE/iX system. Any time a connection exists between a system and one of its nailed devices the same ldev number will belong to that device. Since only nailed devices can be accessed programmatically, all printers must be nailed, as must any devices that will be accessed as programmatic devices at any time. A non-nailed device is a device that is able to establish a connection to an MPE/iX host system but has no permanently assigned ldev number in the NMMGR configuration file of that system. The user of a terminal connected as a non-nailed device can establish a session provided a connection is available and the MPE/iX host configuration specifies a device profile matching the characteristics of the device requesting the connection. When the user logs on to the system, an ldev number is assigned from a pool of available ldev numbers defined through the host system's NMMGR configuration. When the connection is ended (the user logs off) the associated ldev number is returned to the pool of ldev numbers and becomes available for use by a different device connection. The use of non-nailed device connections provides several major advantages. Non-nailed connections simplify the configuration process that must be done on each MPE/iX system, since configuration values do not have to be entered separately. It is possible, if you specify a sufficient number of non-nailed connections on each host, for you to add asynchronous connection capabilities by using the OpenView DTC Manager workstation instead of the host. This prevents you from having to reconfigure your HP 3000 Series 900 computer.
A terminal connected through a DTC on a LAN with multiple MPE/iX or UNIX systems may be configured as a nailed device on more than one host system. Alternatively, it may be nailed on one host system and not nailed on another, or it may be configured as a non-nailed device on all the systems to which it has access. For more information on configuration of asynchronous devices on networks managed by an OpenView network management workstation see the Using the OpenView DTC Manager, as well as Configuring Systems for Terminals, Printers, and Other Serial Devices. |
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