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5730A
Operators Manual
Interface Messages (IEEE-488 Only)
Interface messages manage traffic on the bus. Device addressing and clearing, data
handshaking, and commands to place status bytes on the bus are all directed by interface
messages. Some of the interface messages occur as state transitions of dedicated control
lines. The rest of the interface messages are sent over the data lines with the ATN signal
true. All device-dependent and common commands are sent over the data lines with the
ATN signal false.
IEEE-488 standards define interface messages. Table 6-2 lists the interface messages that
the 5730A Calibrator accepts. Table 6-3 lists the interface messages that the 5730A
Calibrator sends. The mnemonics listed in the tables are not sent as literal statements as
commands are. In this way they are different from device-dependent and common
commands.
Interface messages are handled automatically in most cases. For example, handshake
messages DAV, DAC, and RFD automatically occur under the direction of an instrument
interface itself as each byte is sent over the bus.
Mnemonic
ATN
DAC
DAV
DCL
END
GTL
LLO
IFC
MLA
6-8
Table 6-2. Interface Messages Accepted by the Calibrator
Name
A control line used to notify all instruments on the bus that the next
data bytes are an interface message. If ATN is low, these data
Attention
bytes are interpreted as device-dependent or common commands,
addressed to a specific instrument.
Data
Sets the handshake signal line NDAC low.
Accepted
Data Valid
Asserts the handshake signal line DAV.
Device Clear
Clears the input/output buffers.
A message that appears when the controller asserts the EOI signal
End
line before sending a byte.
Transfers control of the Calibrator from one of the remote states to
Go To Local
one of the local states (See Table 6-8.)
Local
Transfers remote/local control of the Calibrator. (See Table 6-8.)
Lockout
Interface
A control line that sets the interface to a quiescent state.
Clear
Addresses a specific device on the bus as a listener. The controller
My Listen
sends MLA automatically whenever it directs a device-dependent or
Address
common query to a specific instrument.
Function
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