6530 Programmer's Guide

Block Mode Operation
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6530 Programmer’s Guide
Null/Space Handling
In EM3270 mode, nulls sent to the terminal are stored in the buffer at the
current buffer address rather than being discarded.
The following Esc sequences and special keys store nulls rather than
spaces in the screen buffer:
Esc I - Clear to Spaces
Esc J - Erase to End of Page (Ctrl Erase Page)
Esc K - Erase to End of Line/Field (Ctrl Erase Line)
The Read with Address commands (Esc =) and (Esc ]) suppress all nulls
and transmit all spaces, including any trailing spaces.
The delete line (Esc M) sequence stores null characters instead of spaces
in line 24.
The delete character (Esc P) or (Del Char) will store a null instead of a
space in the last character position of the field.
The insert line (Esc L) sequence will store null characters instead of
spaces in the new line.
The insert character (Esc O) or (Ins Home Char) will store a null instead
of a space in the new character position.
Cursor Positioning
In EM3270 mode, the cursor always displays regardless of the presence
of unprotected fields. The cursor position is set by the Set Cursor
Address (DC3) sequence and may be placed in a protected field, an
unprotected field or an attribute location. These rules apply for cursor
positioning controlled by either the host application or the terminal user.
If the user attempts to key data into a protected field or an attribute
location, the audible alarm is sounded and the cursor position remains
unchanged.
The following keys function differently from the 6530 terminal definition
in EM3270 mode:
Arrow keys (up, down, right, left and backspace). These keys
may move the cursor into a protected field or an attribute location.
(Esc A and Esc C perform arrow key functions.)
Tab key. This key moves the cursor to the first character location of
the next unprotected data field. In a display with no unprotected
fields, the cursor is repositioned to row 1, column 1.