HP 3336A - Page 41

Operation
3-20
3-121. Bus Messages. When all the bus operations are organized according to how they are
physically implemented on the HP-IB, twelve unique Bus Messages are found:
DATA
Data Send (to -hp- 3336)
Data Receive (from -hp- 3336)
TRIGGER
REMOTE
LOCAL
LOCAL LOCKOUT
CLEAR LOCKOUT/SET LOCAL
System CLEAR
Management REQUIRE SERVICE
STATUS BYTE
PASS CONTROL
ABORT
STATUS BIT
The Data Message implements the primary purpose of the HP-IB. It is used to send the
codes that activate instrument functions and transfer measurement data from one device to
another. This message is subdivided into Data Send and Data Receive for operator conve-
nience. Technically, there is no difference between Data Messages used to send and receive
information. The Trigger Message causes simultaneous action in two or more devices on the
bus. The action executed depends upon the design of the particular instrument. The
-hp-3336 does not respond to the Trigger Message. The remaining ten Bus Messages are used
to manage the system. Their only purpose is to facilitate the implementation of the Data
Trigger Messages.
3-122. Implementing Bus Messages. Recall that the objective is to answer the question:
‘“‘What instructions must be entered on the controller to cause a
particular action in the instrument?”’
This question is answered by converting the Bus Messages into controller statements that
cause the desired action in the instrument when executed by the controller. Since these
twelve messages describe every possible HP-IB operation, converting them to controller
statements will enable the operator to implement every possible HP-IB operation. A pro-
cedure for converting the Bus Messages to controller statements follows.
NOTE
If the controller used in your system is a -hp- 9825A, Desktop
Computer, substitute the appropriate Bus Message Implementa-
tion Table in Appendix C for Table 3-1. The appropriate con-
troller statements that implement each bus message are given in
this table. If you do make this substitution, be sure to study the
descriptions of the Bus Messages thoroughly. The information
supplied is not restricted to that required to convert the Bus
Messages.
Model 3336A/B/C