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Poll/Select Protocol Support

Poll/Select is a proprietary polled protocol developed by Unisys (Burroughs) or NCR that uses half-duplex async or sync transmissions and multipoint addressing. Poll/Select uses three types of polling:


Specific Poll Each terminal has a unique, two-level address. With a Specific Poll, the terminal only answers polls with the correct address.
Contention Poll This method allows the host to minimize polling overhead. The terminal can send without receiving a poll. This method is used on point-to- point lines (for example: dial connections).
Group Poll/
Group Select		 Poll/Select protocol supports Group Polls and Group Selects when terminals are daisy-chained. Each terminal in the daisy-chain is assigned a Group Poll and Select Address. The host uses the addresses to access a specific terminal in the daisy-chain or all of the terminals.

When a Group function (poll or select) is used, all other terminals with the same Group Address will see the data. When a poll is issued, only the terminal with data to send to the host will respond. The primary terminal (the one next to the modem) determines which terminal can send data. When a select is issued, all other terminals with the same Group Address will receive the data.


Transmission Numbers

Poll/Select terminals use transmission numbers to detect duplicate transmissions. Messages with the same transmission numbers are assumed to be duplicates and are discarded.


Poll/Select Terminals

There are several models of Poll/Select terminals. There are also programs for the PC and Macintosh that can emulate any of the Poll/Select terminals.
Terminal Pages Rows Columns Type Printer Port
TD 830
MT 983
ET 1100
T 27
TT		 One
One
25
75
One		 24
24
24
30
4		 80
80
80
80/132
4		 CRT
CRT
CRT
CRT
Teller		 Shared
Shared
Addressable
Addressable
Shared

All terminals use the same formatting codes. The main difference between the terminals is the number of pages of memory. Normally, applications such as LINC use the first page for data and the second page for error messages (ET 1100 and T 27 only). The TT(Teller Terminal) is a special terminal used for financial applications and does not support screen formatting.


Multi-Environment Capability

The T 27 allows up to three separate windows to be displayed on the same screen. Each window has a different network address.


Multi-Page Support

The ET 1100 and T 27 provide multiple pages. With these terminals, the screen buffer is divided into several pages. The operator can scroll one line at a time through the screen buffer or can move to the next (24 line) segment. The size of each page is determined during setup. The ET 1100 supports up to twelve 24 x 80 pages. The T 27 supports up to seventy-five 24 x 80 pages. The maximum T 27 screen size is 255 rows x 132 columns.


Space Compression

The T 27 supports ANSI space compression for the printer data streams.


Screen Modes

The Poll/Select terminals support two types of screen modes. Each of these modes has several sub-modes which are defined by the application program.
Text Mode This mode supports the entry of video presentation commands and screen formatting commands. Only the video presentation commands are interpreted by the terminal. This mode can be used to design a Forms Modescreen. Any text entered during this mode is sent to the host when the Transmit key is pressed.
Forms Mode This mode interprets both the video presentation and screen formatting commands to display a form as defined by commands in text mode. The transmitted data is dependent on the field types.

Screen Formatting

Poll/Select data streams consist of control codes used to define the Poll/Select protocol. Data formatting codes are used to format the screen display. All of the formatting commands can define the following terminal characteristics:
Screen Formatting Right Justified
Protected Transmittable
Protected Untransmittable
Unprotected
Video Presentation Reverse Video
High Intensity
Secure (non display)
UnderscoreBlink

The T 27 provides a "virtual" 132 column support. The operator can shift the screen to display columns 1 - 80 or columns 52 - 132. Some terminals can display the entire 132 columns on one screen.


Transmission Methods

The Poll/Select terminal supports two transmission types:
Line-at-a-time or blocks

Variable Start and Stop positions (indicated by Start and End markers)

Status Line

The TD 830 and MT 983 terminals use a front-panel LED to indicate a Busy State (Wait Condition). The ET 1100 and T 27 terminals use a Status Line to inform the operator of the terminal's status, network activity, and error conditions. The T 27also provides an Application Status Line which displays messages from host applications.


Print Options

The Poll/Select terminals support three different types of printing:
Shared Buffer The terminal and the printer share a single buffer. The host formats the prints in the buffer while the keyboard is locked, and then sends the buffer to the printer. The TD 830 and MT 983 terminals use this method. The ET 1100 and T 27 can support this method but normally use the next method.
Addressable Printer The terminal has a printer port with its own network address. The host sends the data directly to the printer without disrupting the screen. The ET 1100 and T 27 terminals use this method.
Operator Initiated The terminal operator can send the screen buffer to the printer through a keyboard entry. All of the terminals support this method.

Tab Ruler

The T 27 provides user definable Tab Stops. A Tab Ruler can be displayed on the Status Line to indicate the Tab Stops.

To view the available options that can be specified for this protocol, please review the worksheets. If you need further information on Poll/Select protocol or our implementation and support for this protocol, please e-mail us.