Many hosts use the ASCII (American Standard Code for Information Interchange) character set to simplify communication with other computers; for example, a Digital VAX running VMS, almost all UNIX systems, and Macintosh or PC-DOS systems. You can use either VT102, VT100, VT220, Heath-19, or PC-ANSI emulation with these hosts; the VAX requires one of the VT emulators.
The buttons at the top and left side of the window provide a convenient method of sending frequently used commands to the host with the mouse. You can set the buttons to send a macro instead of the default VT100 control sequences by clicking on the button while holding the Option key down. You can also select text on the screen with the mouse to Copy, Paste, Append, or Print.
If the "Control Controls" dialog item "Show buttons at left of window" is enabled up to 64 "invisible buttons" are available on the left hand side as you move the cursor up and down the left margin of the window. By default, these send key sequences equivalent to the Keypad keys in VT100 Application mode. If the "Control Controls" dialog item "Show status bar at top of window" is enabled you can see the labels for the buttons by moving the mouse over the '?' at the top left of the window.
At the top of the emulator screen there are 11 buttons. By default these perform functions useful with hosts which use ASCII terminals.
Key Function
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CR Enter a line of text or a command.
LF Send an ASCII Line Feed character.
ESC Send an ASCII Escape character.
CTL-S Stop transmission to your terminal.
CTL-Q Restart transmission to your terminal.
DEL Send an ASCII DEL character.
Break Send a break.
CTL-C Usually used to abort a command.
CTL-U Usually used to abort a command.
To the right of the buttons are two counters; the left one shows the packets sent to the network, the right one shows the packets received.
Moving the mouse over a point on the terminal screen will draw a heavy underline beneath that character position; pressing the mouse button will cause dataComet to attempt to move the terminal cursor to the underlined position. (Cursor positioning can be disabled using the "!Ct" macro, or by setting the Single-click macro to an empty macro.) Please note that if you click again while the cursor is still moving, it will not move to the point you expect it to! If the cursor does not go to the proper position on the first mouse click, try it again; the presence of tabs in the text may cause incorrect positioning. When using the UNIX vi editor, you can use "vi cursor motion" to get around this problem, in addition to speeding the process up. ("vi cursor motion" does have a minor problem in that it does not handle wrapped lines properly.)
If you resize a window
You can modify ASCII key mapping using options in the "Control Emulator" dialog; the default keymapping has:
` -> Escape
Backspace -> Delete
Use the Heath-19 emulator and turn on the "Use IBM menus and key mapping" option in the "Control Emulator..." dialog if you want to communicate with an IBM mainframe through the 7171 ASCII terminal adapter. This mode allows you to run programs such as the XEDIT full-screen editor as if you were using an IBM 3278 terminal. Buttons and menu items are provided which allow you to conveniently produce the commands the 7171 accepts as the equivalent of keys on the 3278 terminal. When the 7171 requests your terminal type, type in "C19". (The C19 definition must be loaded into the 7171 configuration for this to work correctly.)
dataComet offers reliable performance with EMACS editor sessions. You can set the meta key using the !CM macro, which you need to associate with a key using a key macro.
This dialog allows you to control the configuration of the emulator for the session which is currently on top when it is an ASCII connection.
"Use IBM menus and key mapping": When you connect to an IBM EBCDIC host indirectly using an ASCII emulator, for example over a modem or Sytek, or through a UNIX machine running tn3270, you can select this option to get key mapping, menus, and controls which send IBM EBCDIC PF keys. You need to use the Heath-19 emulator and choose the TERMINAL TYPE "c19" when logging on over a Sytek or modem connection in order get the host to use the correct key mapping. Choosing this option may disable other ASCII emulation options below.
"Map ` to Escape": Applies to ASCII terminal emulation. Maps the '`' key to the ESCAPE key. (You can still send a '`' by pressing Option-'`'.)
"Map Backspace -> Delete": Applies to ASCII terminal emulation. Makes the key at the top right of the keyboard (variously labeled "Backspace" and "Delete") send a Delete character rather than a Backspace. (You can still send a Backspace by pressing Option-Backspace.)
"Return key sends [] CR followed by [] LF": If the box for CR is checked, return sends a CR; if the box for LF is checked, an LF will be sent. (You can always send a Line Feed by pressing Option-Return.)
"Wrap text when line overflows": Causes lines past the right margin to wrap down rather than being ignored.
"Send vi commands to position cursor": Applies to ASCII terminal emulation when using the UNIX vi editor. This mode allows the cursor to be positioned more accurately and also sends fewer characters.
"Use VT100 jump scrolling mode": Configures the ASCII emulators so that they will not update the screen immediately when the cursor goes above or below the scrolling area, but will wait until all the data from the host has been processed. This can speed up the display with some applications, since scrolling takes a lot of time.
"Don't use Comet-font for characters > 127": By default, dataComet uses the dataComet fonts for all ASCII characters received which are greater than 127. This allows you to use the whole font selected with the "Fonts" Control menu for compatibility with international and other specialized fonts. (Note that the VT100 graphics characters will not appear correctly if this option is chosen; also, this option is set automatically for PC-ANSI sessions.)
Flow Control: XOFF, XON, and KILL characters. dataComet will halt scrolling faster if you set the XOFF character to the character used by your host to temporarily suspend data transmission.
"Answerback": The answerback message dataComet sends the host when it sends a Control-E to dataComet. THIS IS NOT YET SUPPORTED.
"Paste Pacing" options allow you to configure ASCII pastes to work reliably with your host in cases where the host is slow. If "Wait for character echo" is set, dataComet will wait for each character sent to be echoed before sending the next character. If you set "ticks/line," dataComet will pause for that number of ticks (1/60ths of a second) before sending the next line; "ticks/char" pauses for the given number of ticks for each character.
Size: Rows & Columns: You can use these fields to customize the size of the emulator. NOTE that you will have to configure your host to recognize any size other than 24 rows X 80 columns if the host does not accept Telnet window size negotiations. Only emulator sizes with less than 256 rows and total are less than 32000 characters are valid.
The "ASCII" menus come up when you are connected to a host as an ASCII terminal. These show the keyboard mapping for ASCII control keys and key shortcuts. The interpretation of these Control Characters depends on the host and application being used.
dataComet provides an emulation of the IBM 3278 display terminal; it allows you to run programs such as FILELIST or the XEDIT full-screen editor just as if you were using an IBM 3278 terminal. Buttons and menu items are provided which allow the user to conveniently produce the commands produced by keys on the 3278 terminal.
Moving the mouse over a point on the terminal screen will draw a heavy underline beneath that character position; pressing the mouse button will move the terminal cursor to the underlined position. You can also select text on the screen with the mouse to Copy, Paste, Append, or Print. (Note that Paste aborts if the text runs past the end of the current field.)
Key Assignments (see IBM menus also)
Key 3270 Action
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Return ENTER
Shift-Return New Line
Enter PA2
Shift-Enter PA1
Option-Enter CLEAR
Shift-Tab Back-Tab
Backspace Backspace, Delete
The Backspace key changes its behavior when the 3270 emulator is put into "Insert" mode. Ordinarily it produces a backspace-space-backspace, so that the text to the right of the cursor is left in its original position. When Insert mode is ON, the Backspace key will produce a backspace-delete, so that the text to the right of the cursor shifts to the left.
You can also use the Command, Shift, and Option keys to control which action you wish the Backspace to perform. When Command is held down while Backspace is pressed, the character to the right of the cursor is deleted, and the remaining text is shifted left. When the Option key is held down, the result is a backspace-delete, as is the case in Insert mode. When the Shift key is held down, the standard backspace-space-backspace will be produced.
If the "Control Controls" dialog item "Show buttons at left of window" is enabled 64 "invisible buttons" appear on the left hand side as you move the cursor up and down the left margin of the window. By default, these send the PF keys from 1 through 24. If the "Control Controls" dialog item "Show status bar at top of window" is enabled you can see the labels for the buttons by moving the mouse over the '?' at the top left of the window.
If the "Control Controls" dialog item "Show status bar at top of window" is enabled, there are 11 buttons at the top of the emulator window which perform actions available on 3270-type terminal keys:
Button The Usual Effect
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Enter Enter a line of text or a command.
PA1 Programmed Attention-1 (Toggles CP-mode).
PA2 Advance screen from "MORE..." or "HOLDING".
Clear Advances screen from "MORE..." and clears the
input area.
Insert Go into Insert mode (inserts characters at
the cursor as long as there are spaces
at the end of the current field).
Reset Cancel Insert or clear KBD-lock (KBD-lock is
displayed on the right side of the screen).
Home Move the cursor to the top left of the screen.
E Inp Erase the input area.
E EOF Erase from cursor to End of Field.
PA3 Programmed Attention-3 (application-defined).
DEL Delete the character at the cursor position.
To the right of the buttons are two counters; the left one shows the packets sent to the network, the right one shows the packets received. If you are using Telnet, the counter on the left may appear reversed (white on black)--this indicates that MacTCP is resending the packet to the host.
A "HOST BUSY" indicator appears at the top of the screen when one the host system is busy processing your command; the host will not accept new commands from an Enter or PF key until the "HOST BUSY" indicator goes off.
IMPORTANT NOTE: You can enhance your communications efficiency when using the 3270 emulator by making sure that XEDIT has "SET FULLREAD OFF" in your PROFILE XEDIT file; XEDIT-based applications such as RICEMAIL may need to have this option turned off also to get optimal performance. FULLREAD mode causes an extra 2,000 bytes to be sent with every PF-keystroke in the Action menu, and can significantly degrade performance on slower networks such as LocalTalk.
This dialog allows you to control the configuration of the session which is currently on top when the connection is made using the 3270 emulator.
"Typeahead: allow input when System Busy": The Typeahead option in the Control Menu allows you to set the emulator so it will discard all input when the SYS (system lock) light is on, as would a genuine IBM 3270 display. Thus, if typeahead is turned off, for a moment after the Enter key or a PF key is pressed, no input will be accepted from the keyboard, and all pending keyboard events will be discarded. If typeahead is on, keyboard input will be discarded only in the event of a "keyboard lock" condition, signified by the KBD light on the right of the screen, or if an error occurs in processing a command. (Note that when the Keyboard lock condition occurs, it can be cleared by either pushing the Reset button or executing the Reset menu command.)
The IBM 3270 video display terminal distinguishes between null characters and spaces, yet displays both as blank spaces. Because this distinction fails to deliver "what you see is what you get," we have two menu options for handling nulls.
"Send Imbedded 3278 Nulls as Blanks": Causes the emulator to substitute blanks for nulls which are in the middle of text within a field.
"Squeeze out blanks at end of field in Insert mode": Causes blanks to be treated like nulls so that blanks at the end of a field will be deleted as you insert text in the middle of the field.
"Shift whole field when deleting characters": Causes the whole field, rather than just the portion of the field on the current line, to shift to the left when a character is deleted.
"Use starting cursor position as margin when pasting": Causes pastes to move the cursor back to the original starting column on the next row rather than to the beginning of the next row.
IBM Terminal Type: Allows you to set screen sizes other than the standard 24 row by 80 column display. NOTE that not all applications will use the larger display area.
The "IBM" and "Action" menus come up when an IBM terminal session is being performed. These menus show the keyboard mapping and key shortcuts.
"IBM": This menu contains Local keys which move the cursor and modify the screen without notifying the host of any changes.
"Action": This menu contains Program Function (PF), Program Attention (PA), and other keys will send the current screen to the host and signal the host to interpret the screen. The interpretation of these "PF keys" varies depending on the application.
