Giga-tronics 8003, Operation Manual

Page: 167 / 258

Remote Operation
Manual 20791, Rev. C, June 2001 3-25
3.3.17 Key Stroke Emulation Enable/Disable Command Structure
KEYEM, KE
Syntax: KEYEM hs modifier
Modifiers: This modifier turns on the key stroke emulation mode.
Modifier name: ON,+
Modifier Syntax: ON
This modifier turns off the key stroke emulation mode.
Modifier name: OFF,-
Modifier Syntax: OFF
Description: Key Stroke Emulation is a feature that allows the GPIB controller to access 8003 functions
that are not available through normal GPIB commands. This is a special mode wherein a
sub-set of ASCII characters are interpreted as the 36 keys on the front panel of the 8003
(see Figure 3-1 on page 3-1).
There are two completely separate methods for entering and exiting the key emulation
mode which cannot be interchanged. In the first method, the controller sends a KEYEM
ON command and then asserts a global local. The GPIB 488 REN line is sent false and all
characters are passed on as key strokes, just as if they were entered from the front panel.
It should be kept in mind that once the key emulation mode is turned on, any commands
sent to the 8003 while it is in local (remote enable line false) will be interpreted as a key
stroke. It is still possible to program the instrument in remote while the key emulation
mode is enabled. This is done by placing the 8003 in remote (remote enable set true and
listen addressed). This allows the host controller to switch between the true remote state
and the local key stroke emulation mode without disabling the key stroke emulation mode.
The feature is disabled by sending a KEYEM OFF command.
Although the above method is easy to do and will work no matter what data must be sent
to the 8003, it does require the controller to place all of the instruments on the bus in the
local mode with the global local command. This can cause certain devices to change their
settings which might not be desirable.
The second method does not require the entire bus to go into the local mode. It can be
accessed as described above but, instead of a global local command, a device specific go
to local command is used. Characters will then be treated as key strokes until a reserved
character [in this case an asterisk (*)] is received to exit the key emulation mode and start
converting characters back into normal GPIB commands. Under the circumstances
described in #2 on the next page, the timing of the * character must be programmed so as
not to prematurely abort some keyboard emulation function that might still be in process.
This means that if the buffer were full with 16 characters, the routine would not see the *
reserved character and would continue to try and interpret GPIB commands as key
strokes.