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HP-IB
Bus
Structure
pg635d
Able to talk
DEVICE D
Able to
talk only
I
DATA 8US (8 signal lines)
, HANDSHAKE LINES
Figure 11-2. HP-IB Bus Structure
Data
Bus
The data bus consists of 8 bidirectional lines that are used to transfer data from one device to
another. Programming commands and data transmitted on these lines are typically encoded
in ASCII, although binary encoding is often used to speed up the transfer of large arrays.
Both ASCII- and binary-data formats are available to the analyzer. In addition, every byte
transferred over HP-IB undergoes a handshake to insure valid data.
HandshakeLines
A three-line handshake scheme coordinates the transfer of data between talkers and listeners.
lb
insure data integrity in multiple-listener transfers, this technique forces data transfers
to occur at the transfer rate of the slowest device connected to the interface. With most
computing controllers and instruments, the handshake is performed automatically, making it
transparent to the programmer.
Control Lines
The data bus also has five control lines The controller uses these lines to address devices and
to send bus commands.
IFC (Interface Clear)
This line is used exclusively by the system controller. When
this line is true (low), all devices (whether addressed or not)
unaddress and revert to an idle state.
CompatiblePsripherals
11-17