6530 Programmer's Guide

6530 Programmer’s Guide 3-1
3
Block Mode Operation
In block mode, the 6530 transmits data to and receives data from the host
in blocks. The 6530 is always ready to receive blocks from the host;
however, it only transmits a block when:
The host application sends a control code or escape sequence that
requests data from the 6530, (for example; Esc a (Read Cursor
Address).
The host application issues a read operation and the user presses a
function key; in which case, the 6530 transmits a function key
message to the host.
Block mode allows users to perform local editing operations (such as
inserting or deleting characters) before the data is transmitted. In
addition, protect submode allows your application to control the format
of data on the screen and the type of characters that can be entered from
the keyboard.
Display memory in block mode is organized into logical pages. Each
page has its own cursor and buffer address. All keyboard operations take
place on the currently displayed page at the cursor location. Your
application program can select a page for I/O independently of the
displayed page. Except for explicit cursor movement operations, your
application program accesses memory on the selected page through the
use of buffer addresses rather than cursor locations.
This section provides detailed descriptions of fields and field attributes
(for protect submode), control codes and escape sequences, function keys
and other keyboard operations available in block mode operation.
Fields and Field
Attributes (Protect
Submode)
In protect submode, your application can subdivide a page into fields.
A field is defined as an area of positions on a page having the same data
attributes. A field can be of any length from one cursor position up to the
size of the page; thus, a field can span lines but it cannot cross page
boundaries.