6530 Programmer's Guide

Conversational Mode Operation
6530 Programmer’s Guide 2-7
where:
SOH is a control character (01H) that acts as a start of header for
messages returned to the host.
The underscore (_) identifies this message as a cursor address
message.
The exclamation point (!) specifies page 1. (Page 1 is always used in
conversational mode.)
row and column are encoded ASCII characters that specify the
current cursor location.
CR is a control character (0DH) that terminates the message.
Cursor Movement This group of control codes and escape sequences moves the cursor on
the screen. The cursor cannot be moved off the screen. Attempts to move
the cursor off the right side of the screen result in the cursor wrapping to
the first column of the next row. Attempts to move the cursor off the left
side of the screen result in the cursor wrapping to the last column of the
previous row.
Attempts to move the cursor off the top of the screen result in an
automatic roll down operation. The roll down operation moves the display
memory lines down one row on the screen so that one line of memory
rolls off the bottom and a new line appears at the top. When the first line
of display memory appears at the top of the screen, further roll down
operations are inhibited.
Attempts to move the cursor off the bottom of the screen result in an
automatic roll up operation. The roll up operation moves the display
memory lines up one row on the screen so that one line of memory rolls
off the top and a new line appears at the bottom. When the bottom row
contains the last line of display memory, a scroll operation occurs. The
scroll operation deletes the first line of display memory, moves all
remaining memory lines up one line (so that the former second line of
display memory is now the first line of display memory, and so on), and
inserts a new blank line at the end of memory. This line is then rolled up
onto the last row of the screen.
Cursor Up (Esc A)
The Esc A sequence moves the cursor up to the previous row, while
maintaining the same column position. If the cursor is initially in row l,
a roll down operation occurs unless the first line of display memory
already appears on the screen.