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The following modes affect the transmission of data from the terminal's display memory to the host. Their settings can be reviewed, and changed as desired, on the Setup lines; see Setup section. The Setup line letter, and mode number, are shown in parentheses following the name. Detailed descriptions of these modes can be found in the Appendix.
zTPDM Transfer Pointer Display Mode (A,41). During a transmission, the cursor symbol is not displayed (since the keyboard is disabled). This mode permits a transfer pointer symbol to be displayed (as feedback to the operator that the terminal is in the transmit state and that transmission is occurring).
zAKDM Auto Keyboard Disable Mode (B,46). Upon completion of a transmission, the keyboard is automatically re-enabled (and the cursor symbol returns). This mode permits the keyboard to remain disabled, until purposefully released by the host with an EMI control.
zLTM Line Transfer Mode (B,42). A transmission normally continues until completion. For hosts that cannot buffer a full Page, this mode permits the terminal to stop transmitting at the end of each line (requiring the host to send a DC1-code (1/1) to obtain the next line).
NOTE: The terminal will respond normally, in all modes, to a DC1/DC3 protocol (or use of the Clear-to-Send interface signal) to start/stop transmission.
TTM Transfer Termination Mode (B,16). A transmission will normally terminate after sending the character at the cursor position. This mode permits the transmission to continue to end of Page.
zGRTM Graphic Rendition Transfer Mode (B,45). The characters in the Page are normally transmitted without information regarding their rendition. This mode permits this information to be transmitted, by including the necessary SGR controls in the transmissions.
GATM Guarded Area Transfer Mode (B,1). Areas of the Page may be designated as guarded (i.e. their contents are not normally to be transmitted); see Forms section. This mode permits the contents of these Areas to be included in the transmissions.
The following modes permit trailing Space codes (2/0) to be suppressed in the transmission.
FETM Format Effector Transfer Mode (B,14). Permits trailing Spaces to be suppressed at end of line (if FETM is reset). A New-Line code is inserted to mark their omission. LNM (LF New Line Mode) selects CRLF (LNM reset) or LF (LNM set) as the New-Line code.
zCSTM Column Separator Transfer Mode (B,43). Permits trailing Spaces to be suppressed at each Columnar tab stop. An HT-code (0/9) is inserted to mark their omission.
zFSTM Field Separator Transfer Mode (B,44). Permits trailing Spaces to be suppressed at each Page tab stop. An HT-code is inserted to mark their omission.
The following modes permit Selected Area transmission; see Using Selected Areas below.
SATM Selected Area Transfer Mode (B,17). Permits transmission of the Active Selected Area (if SATM is reset).
MATM Multiple Area Transfer Mode (B,15). Permits transmission of all Selected Areas in the Page (if SATM is reset).
Operator Control. The operator will normally initiate transmission with the SEND key. The SEND key controls two programmable strings; see Programmable Strings section.
One is active during Simultaneous SRM (i.e. normal conversational entry). It is initialized to null at power-on. It can be programmed with whatever control string is desired (and can be accommodated by the host); see Using the Transfer Pointer, below. If the string is always wanted, the programmable Power-on string may be used to load the key with the string each time the terminal is powered on.
The other string is active during Monitor SRM (i.e. off-line entry). It is initialized with the STS control at power-on. When the key is typed, transmission starts at the top of the Page and terminates with the cursor (TTM reset) or end of Page (TTM set). The content of the transmission, whether a transfer pointer is displayed, etc. is determined by the various modes; see above. The key can likewise be re-programmed with other control strings that the user might find useful.
Host Control. The host initiates transmission with the STS control.
STS Set Transmit State (ESC S). Initiates transmission (provided the
terminal's communications interface is ready; see Flow Control of
Transmitted Data below). The transmission starts at the top of Page and
terminates with the cursor (TTM reset) or end of Page (TTM set). The region
transmitted can be narrowed (to as small as a single character) with
the zSTP and zSTE controls; see Using the Transfer Pointer. Sub-regions
may be excluded from the transmission; see Using Guarded Areas and Using
Selected Areas.
The transmission of data from the terminal's memory to the host is controlled by two flags in the terminal and a communications input.
A Transmit Ready Flag (TRF) indicates that transmission is desired. It is set by the STS control, whether entered by the operator or received from the host. It is reset at power-on and at the end of each transmission. It may also be reset by the operator with the BREAK or SETUP keys, or by the host with the INT control; see Aborting a Transmission below.
A Communications Ready Flag (CRF) indicates that the communications interface is ready to send the data. It is set at power-on. It can be set and reset by the host with the DC1 (1/1) and DC3 (1/3) controls. If zLTM is set, it is automatically reset after each line is transmitted.
A Clear-to-Send (CTS) input signal at the communications connector (pin 5) indicates that the external communications system is ready to accept the data. This input may be controlled by the external system, or it may be left open (if the external system is always ready); see Checkout & Installation section.
All three conditions must be ready for transmission to occur. Therefore, the actual transmission may be initiated by any one of the conditions by first setting the others. The transmission may be suspended by resetting CRF or by pulling the CTS input low. The transmission may be terminated only by resetting TRF.
Operator Control. The operator may abort a transmission by typing the BREAK or SETUP key.
Host Control. The host may abort a transmission by sending the INT control.
INT Interrupt (ESC a). Terminates a transmission in progress.
NOTE: This control is detected at the input of the terminal's FIFO buffer. The host may send other controls during the transmission (to be executed upon completion of the transmission) without interfering with its ability to abort the transmission.
If a trailer string has been programmed (see Header and Trailer Strings below), aborting a transmission aborts only the text portion of the transmission; the trailer string is still sent.
The Ambassador provides programmable Header and Trailer strings; see Programmable Strings section. Both are initialized to null at power-on. If programmed, the Header string precedes, and the Trailer string follows, all STS-initiated transmissions. Example:
ESC P ` Sp ~ B | ~ C ESC \
This string programs an STX (0/2) into the Header string and an ETX (0/3)
into the Trailer string. All STS-initiated transmissions will now begin
with an STX and end with an ETX.
ESC P ~ [ P { @ } Sp { ^ } B { \ ^ } C ~ [ \ ESC \
This string programs the preceding string into the programmable Power-on
string, so that the string is executed each time the terminal is powered
on.
Transmission normally starts at the beginning of Page, and ends with the cursor (TTM reset) or end of Page (TTM set). The Ambassador provides two controls that permit the starting and ending points to be specified anywhere within the Page.
zSTP Set Transfer Pointer (ESC [ Pn1 ; Pn2 u). Sets the starting address
of the transfer pointer to line Pn1, column Pn2. The transmission includes
the character at this position. The default value (for line and/or
column) is the present cursor position.
zSTE Set Transfer End (ESC [ Pn1 ; Pn2 z). Sets the ending address of
the transfer pointer to line Pn1, column Pn2. The transmission includes
the character at this position. The default value (for line and/or
column) is the present cursor position. Note: If TTM is reset (i.e.
transmit to cursor), if the cursor is encountered before reaching the
specified endpoint, the transmission will terminate after transmitting the
character at the cursor. This may be avoided by setting TTM.
Examples:
ESC [ u ESC [ z ESC S
This string transmits the character at the cursor. If a Header and
Trailer string are programmed, they will precede and follow the character.
ESC [ ; 1 u ESC [ ; 80 z ESC S
This string transmits the entire contents of the active line (i.e. the
line containing the cursor). If FETM is reset, any trailing spaces
are suppressed and the transmission is terminated with the new-line
character selected by LNM. Alternatively, FETM may be set and the
new-line character programmed into the Trailer string.
ESC P ` " ~ [ [ ; 1 { U } ~ [ [ ; 8 0 { Z } ~ [ S ESC \
This string programs the preceding string into the SEND key to provide
a Line Transmit function during Simultaneous SRM. The contents of the
active line are now sent to the host whenever the SEND key is typed.
ESC [ ; 2 u ESC [ ; 80 z ESC S
If your system uses a 1-character prompt, this string transmits the
line without transmitting the prompt.
ESC [ 6 ; 1 u ESC [ 12 ; 80 z ESC S
This string transmits the contents of lines 6 through 12 of the Page.
Note: The preceding example could also have been done using the zSDP
control. The zSDP control defines the 'Page'. It partitions memory,
but does not change its contents; see Display section, Definitions.
The STS control sends only the contents of the Page (TTM set). The
string, ESC [ 12 ; 5 p ESC S, would have accomplished the same function
with fewer codes (ignoring the fact that the Page still has to be
restored). The transfer pointer controls are more versatile (because
they permit column parameters).
The Ambassador provides a Selected Area capability that permits the region(s) of the Page (to be transmitted) to be selected by visible symbols in the display. A Selected Area is defined as starting with an SSA symbol (forward-pointing triangle) and ending with an ESA-symbol (backward-pointing triangle).
The operator can enter (or insert) these symbols with the SSA and ESA keys on the Control keypad. The host enters them with the SSA and ESA controls.
SSA Start of Selected Area (ESC F). Writes an SSA-symbol to the Page.
ESA End of Selected Area (ESC G). Writes an ESA-symbol to the Page.
These symbols are characters, just like any of the other graphic characters. They may be erased with erase controls, moved with edit controls, and are included in transmissions (as their escape sequence).
The symbols assume a control attribute only when SATM is in the reset state. In that case, they affect the transmission according to the setting of MATM.
If MATM is reset, only the active Selected Area (i.e. the one containing the cursor) is transmitted. If TTM is reset (i.e. transmit to cursor), the transmission includes the SSA-symbol and all following text through the character at the cursor.
If MATM is set, all Selected Areas in the Page (or up to the cursor, if TTM is reset) are transmitted. The contents of each area are bracketed by SSA and ESA symbols in the transmission.
The Ambassador provides a Guarded Area capability that permits designated regions in the Page to be 'guarded' from transmission. The regions are designated by the host with the DAQ control; see Forms section. They are normally intended for use with Forms, but may also be used by the host simply to exclude designated regions of the Page from the transmission. Example:
ESC [ 6 H ESC [ 1 o ESC [ 9 H ESC [ o ESC S ESC [ 60 p
This string excludes lines 6-8 of the Page from the transmission and restores
the Page (to 60 lines).
NOTE: Selected and Guarded Areas provide alternative means of accomplishing the same result, namely selective transmission of designated regions of the Page. It is envisioned that the operator will tend to use Selected Areas (because of the visible symbols) and the host Guarded Areas. Using the two types of areas in combination is not recommended. Doing so will yield predictable, but not necessarily sensible, results.