GPIB
370B User Manual
4-11
The address setting can be verified or changed by examining or setting the
address switches located on the rear of the 370B (see Figure 4–3).
The address can also be verified by simultaneously pressing the front panel
FAST/SHIFT and LOCAL keys. The message terminator and bus address appear
in the error message area of the 370B.
Choosing the Message Terminator. The terminator is used to indicate the end of a
message transfer. The two most common terminators are the EOI (end or
identify) signal line and the LF (line feed) character.
If EOI is selected, the 370B will assert the EOI line simultaneously with the last
data byte when sending a message, and will recognize the EOI line as the
terminator when receiving a message. If LF is selected, a CR (carriage return)
and LF (line feed) are sent following the last data byte, The EOI line is asserted
simultaneously with the LF character.
When receiving a message, the 370B will terminate the message upon receiving
either the LF character or the assertion of the EOI line.
The best way to determine which terminator to use is to look at the specifications
for the system controller and use the same terminator. For the Tektronix 4041
and the HP 200/300 Series, this would be the EOI terminator.
The terminator can be set with the terminator switch on the rear panel configura-
tion switch bank (see Figure 4–3).
Reading in the Switch Settings. The switch settings are read by the 370B’s
processor only at power–up or when the message terminator and bus address are
displayed on the CRT. Therefore, when switches are changed while the power is
on, simultaneously press the FAST/SHIFT and LOCAL keys to make the switch
change effective.
Attach the 370B to the GPIB with a standard GPIB cable. A GPIB system may
be connected in two general configurations: star or line. While the star configura-
tion is recommended, configurations can be mixed as long as the total cable
length does not exceed 20 meters and the instruments are distributed on the bus
according to a few basic rules (see Figure 4–4).
First, no more than 15 total devices, including the controller, can be included on
a single bus. In addition, to maintain proper electrical characteristics, one device
load must be connected for every two meters of cable. Generally, each instru-
ment represents one device load on the bus. The 370B represents one device
load.
Connecting the GPIB
Cable
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General