6530 Programmer's Guide

Block Mode Operation
6530 Programmer’s Guide 3-15
Read Cursor Address (Esc a)
The Esc a escape sequence causes the 6530 to transmit the cursor address
for the currently selected page. The message returned to the host uses
normal addressing and has the following general format:
SOH _ page row column terminator
where:
SOH is start of header (01H).
The underscore (_) identifies this message as a cursor address
message.
page is an ASCII character whose code offset by 20H specifies the
page number of the currently selected page.
row and column are encoded ASCII characters that specify the
current cursor position.
terminator comprises the control characters ETX (03H) and
LRC (Longitudinal Redundancy Check) in block mode.
In protect submode, the cursor will not be displayed on the screen if there
are no unprotected fields in the page. In this case, the cursor position
indicates that the cursor is in line l, column 1 of the page. because it is
impossible for this position to be unprotected, this address can be used to
detect the condition.
Note In EM3270 mode, the cursor is always displayed, regardless of
the presence of unprotected fields.
Set Buffer Address (DC1)
The DC1 control character (11H) sets the buffer address for the selected
page, using normal addressing (as described in “Cursor and Buffer
Addressing” on page 3-13). This buffer address acts as the starting
address for the next I/O operation directed to the page, such as a read or
write operation. You can use this control sequence to access any position
up to 80 columns. The DCl character must be followed by two encoded
ASCII characters that specify new row and column positions for the
buffer address. For example, the following sets the buffer address to row
5, column 2:
11H $ !