XITRON 2000I, Руководство пользователя

Страница: 80 / 96

80
2000I & 2000M User Guide, Rev B
Bus Commands
As previously mentioned, the IEEE488 interface can perform many tasks that
the RS232 does not, those used by the 2000 instrument are as follows:
1. Remote/Local Selection. This has been previously described.
2. Device Clear capabilities. The IEEE488 defined Device Clear functions
(both selective and global) force the 2000 to perform a power-on reset
function.
3. Serial Poll capabilities. The IEEE488 defined serial poll capabilities of
the 2000 correspond to the requirements of the IEEE488 standard, the
response byte transmitted by the 2000 consisting of 2 bits of information,
the remaining 6 bits all being returned as logical 0. The next to most
significant bit (with a decimal equivalence of 64) is set if the 2000
instrument is actively asserting the IEEE488 SRQ line, and the least
significant bit (with a decimal equivalence of 1) is set if the 2000 has
completed actioning the previously received command string
4. Interface Clear capabilities. The IEEE488 standard defines this
command, which causes the interface portion of the 2000 instrument to
be reset to the power on conditions, aborting any bus activity in progress.
5. Parallel Poll capabilities. The 2000 instrument does not have any Parallel
poll capabilities.
Other IEEE488 Specific Items
Should a handshake sequence be improperly completed during a transfer of
data to or from the 2000 interface, then the 2000 instrument will
automatically perform a power on reset sequence. This facility prevents the
interface becoming locked out should the interface cable be removed or
become faulty during a data transfer.
Also note that the 2000 instrument offers the facility of changing the
IEEE488 address via the front panel or via the interface. To protect the
interface from entering an undefined state when this occurs, the 2000
instrument will automatically perform a power on reset sequence when this
occurs.