Martel Electronics 3001 - Manual (Page 44)

or via the IEEE-488 message LLO (Local Lockout), the 3001 front panel
controls are totally locked out. The left end of the top line of the display
changes to: rem.
To return the 3001 to the local with lockout state, send the RS-232 LOCAL
command or the IEEE-488 GTL (Go To Local) message.
Table 4 summarizes the possible operating state transitions. For more information on
IEEE-488 GPIB messages, see section 9.5.
Table 4 - Operating State Transitions
From To Front Panel GPIB Message Serial Command
Local Remote MLA (REN True) REMOTE
Local with Lockout LLO LOCKOUT
Remote Local Local 0 key GTL or REN False LOCAL
Remote with Lockout LLO LOCKOUT
Local with Local REN False LOCAL
Lockout Remote with Lockout MLA (REN True) REMOTE
Remote with Local REN False LOCAL
Lockout Local with Lockout GTL
9.5 IEEE-488 Interface Overview
The IEEE-488 parallel interface sends commands as data and receives measurements
and messages as data. The maximum data exchange rate is 1 Mbyte per second, with a
maximum distance of 20 meters for the total length of the connecting cables. A single
cable should not exceed 4 meters in length.
Several commands are used only for RS-232 serial operation because these functions
must be implemented as IEEE uniline (single control line) bus management messages
per the IEEE Standards. For example, the command REMOTE could be sent as data
over the IEEE-488 interface to place the 3001 into remote operating mode, but it is not
because the IEEE Standards call for the remote function to be sent to the device as the
uniline message REN. This is also true for several other commands and functions, as
shown in table 5 below with their RS-232 equivalents.
Table 5 - RS-232 Emulation of IEEE-488 Messages
IEEE-488 Message RS-232 Equivalent
GTL LOCAL command
GTR REMOTE command
LLO LOCKOUT command
SDC, DCL (not emulated on RS-232)
GET (not emulated on RS-232)
SPE, SPD (not emulated on RS-232)
UNL, UNT (not emulated on RS-232)
The IEEE-488 interface is based on the IEEE Standards 488.1 and 488.2. For detailed
information, refer to the IEEE-488.1 and IEEE-488.2 standards.
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