6530 Programmer's Guide

Block Mode Operation
6530 Programmer’s Guide 3-71
Read Keyboard Latch (Esc - o)
The Esc - o sequence enables the host application to determine if the user
has issued any data keystrokes since the last keyboard unlock. The
keyboard latch is reset each time the terminal receives an Unlock
Keyboard (Esc b). The latch is set anytime the MDT bit of an unprotected
field is set due to a keystroke. The latch may be read by using the
following sequence. The format of the sequence is as follows:
Esc - o
The terminal replies with a message of the following format:
SOH < char terminator
where:
SOH is a control character (01H) that acts as a start of header for
messages returned to the host.
< is an ASCII < (%074) and identifies the keyboard latch message
char is one of the following:
0 (30h) = The latch is reset
1 (31h) = The latch is set
terminator comprises the control characters ETX (03H) and
LRC (Longitudinal Redundancy Check) in block mode.
PFKey Performance Feature
When the PFKey feature is enabled, the device returns the function key
sequence plus all modified fields in a single transmission in response to a
read operation by the Tandem host application. In effect, the fields
returned are the response to a Read with Address (Esc = SP SP 7 o) as
follows:
STX SEQ# keycode page cursor read-with-address-
data ETX LRC
The PFKey mode is disabled when entering protect submode or when
executing a reinitialize command. This will protect a PFKey-unaware
application.