6530 Programmer's Guide

Block Mode Operation
3-44
6530 Programmer’s Guide
Example 5:
Two special cases also occur:
The default field (line l, column l) is not returned unless it is
explicitly defined by a start field sequence (GS control character or
Esc [ sequence), even if the read start address is at line 1, column 1.
When the last position on the page is a start-field address (video
attribute character) nothing is returned for that field.
Read Whole Page / Buffer (Esc <)
The Esc < sequence reads the contents of either the entire selected page
(nonprotect submode) or all unprotected fields in the selected page
(protect submode).
In protect submode, the text transmitted consists of the data stored in all
the unprotected fields, regardless of whether these fields have their
MDTs set. The transmission starts with the first unprotected field on the
selected page and continues through the last unprotected field on the
page.
Note In EM3270 mode, a screen with no fields is treated as a single
unformatted field. Data can be keyed at any character position. This
escape sequence handles such a screen by transmitting any character
position not containing a null. These data are
not preceeded by a DC1
row column sequence.
In EM3270 mode, if there is no attribute at row 1, column 1, the last
field on the screen wraps around to include any characters preceding
the first attribute location on the screen. This command sequence
handles such a field by sending a DC1 command, followed first by a
two byte address, then the data at the bottom of the screen, and the
data at the top of the screen.
The video and data attributes of the last field on the screen are also
enforced for the positions at the top of the screen. This will effectively
override the Set Video Prior (Esc 7) setting.
F1 F2 F3 F5F4
Sends data from
F2, F3, and F4
read start address
(beginning of F2)
read end address
(beginning of F5)