Tektronix PFG 5105, Instruction Manual

Page: 74 / 89

(
(
SPE - Serial Poll Enable (24 with ATN)
The SPE message enables the instrument to supply
output serial poll status bytes when it is tal k
addressed.
SPD - Serial Poll Disable (25 with ATN)
The SPD message switches the instrument back to
its normal operation of sending the data from the
Output Buffer.
MLA - My Listen Address (Address
+
32)
MTA- My Talk Address (Address
+
64)
The primary listen and talk addresses are established
by the instrument IEEE-488 bus address (set by
front-panel key sequence). The current setting of the
bus address ID displayed on the front panel when
the INST ID key is pressed. When the instrument is
addressed to talk or listen, the front panel AD­
DRESSED indicator is lighted.
LLD - Local Lockout (17 with ATN)
In response to LLO, the instrument changes to a
lockout state-from LOCS to LWLS or from REMS to
AWLS.
REN - Remote Enable (GPIB pin 1 7)
If REN is true, the instrument may change to a remote
state (from LOCS to REMS if the internal message
return-to-local (rtl) is false, or from LWLS to AWLS)
when its listen address is received. REN false causes
a transition from any state to LOCS; the instrument
stays in LOCS as long as REN is false.
A REN transiton may occur after message processing
has begun. In this case, execution of the message
being processed is not affected by a transition.
GTL -Go To · Local (1 with ATN)
Only instruments that are listen-addressed respond
to GTL by changing to a local state. Remote-to-local
transitions caused by GTL do not affect the execution
of the message being processed when GTL was
received.
Remote-Local Operation
The preceding discussion of interface messages des­
cribes the state transitions caused by GTL and REN.
Most front panel controls cause a transition from
REMS to LOCS by asserting a message called return­
to-local (rtl). This transition may occur during message
execution; but, in contrast to GTL and REN transitions,
PFG 51 05/5505 Instruction Manual
Programming
a transition initiated by rtl does affect message ex­
ecution. In this case, the instrument generates an
error if there are any unexecuted setting or operational
commands. Front panel controls that change only the
display (such as INST ID) do not affect the remote­
local states -only front panel controls that change
se t tings assert rtl. The rtl message remains asserted
while multiple keystroke settings are entered, and it
is unasserted after the execution of the settings. Since
rtl prevents transition to REMS, the instrument unas­
serts rtl if a multiple key sequence is not completed
in a reasonable length of time (approximately 5 to
10 seconds).
The instrument maintains a record of its settings in
the Current Settings Buffer and new settings from the
front panel or the controller update these recorded
settings. In addition, the front panel is updated to
reflect set t ing changes causes by commands. I nstru­
ment settings are unaffected by transitions among the
four remote-local states. The REMOTE indicator is
lighted when the instrument is in REMS or AWLS.
Local State (LOCS)
In LOCS, instrument settings are controlled by the
operator via front panel keys. When in LOCS, only
bus commands that do not change instrument settings
are executed (query-output commands.) All other bus
commands (setting and operational ) generate an
error since those functions are under front panel
control.
Local Without Lockout State (LWLS)
The instrument operates the same as it does in LOCS,
except that rt l will not inhibit a transition to remote.
Remote State (REMS)
In this state, the instrument executes all instrument
commands. For commands having associated front
panel indicators, the front panel is updated when the
commands are executed.
Remote With Lockout State (RWLS)
Instrument operation is similar to REMS operation
except that the rt l message is ignored. (The front
panel is locked out.)
3-29 .