6530 Programmer's Guide

Block Mode Operation
6530 Programmer’s Guide 3-13
Cursor and Buffer
Addressing
This group of control codes and escape sequences sets new locations for
the cursor and buffer addresses on the selected page. Each page has its
own cursor address and buffer address, which can be the same or different
for each page. You can change the cursor or buffer address on one page
without affecting the addresses on other pages.
Your application accesses memory on the selected page through either the
cursor address or the buffer address for that page. Operations that involve
explicit cursor movement, such as a backspace or line feed, use the
current cursor address for the selected page. Other operations, such as
reads and writes to the selected page, use the current buffer address for
that page.
Both the cursor and buffer addresses are specified by row and column
positions. The home location (upper, left corner) is row l, column 1. The
address can take one of two forms, called normal and extended
addressing.
In normal addressing, the row and column positions are specified by
encoded ASCII characters whose codes, offset by IFH, represent the
positions. For example, the home cursor location (row 1, column 1) is
specified by two ASCII space characters (20H). The next location (row 1,
column 2) is specified by a space character (20H) and a ! character (21H).
Valid row positions are encoded in the range of 20H through 37H; valid
column positions are encoded in the range of 20H through 6FH. A
character outside of this range causes a command error to occur.
In extended addressing, the row and column positions are specified by
decimal numbers represented as a string of ASCII characters. The row
and column numbers are separated by a semicolon (;). Row position
values greater than 24 and column values greater than 80 are interpreted,
but default to 24 and 80, respectively
In protect submode, the cursor cannot be positioned into a protected field
from either the keyboard or your application program. However, the
buffer address can access any area of the page. Thus, your application can
write to or read from any field.