HP 5335A - Page 47

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Operation and Programming
LISTEN:
SERVICE REQUEST:
REMOTE/LOCAL:
PARALLEL POLL:
DEVICE CLEAR:
DEVICE TRIGGER:
CONTROLLER:
3-159. Bus Messages
When addressed as a Listener, the instrument can accept any
number of commands from a controller on the bus. These
commands will usually be used to program the instrument
operation.
SRQ can be sent out to the bus at the end of measurements and
on error or failure messages. Normally SRQ is inhibited, but
certain commands will enable this feature. See "WA” and "SR”.
Normally the 5335A is under local control. In order to program
the instrument it must be in Remote. Once in Remote, all pro¬
grammable controls are in remote and cannot be affected by
manual command. The RESET key may be used to manually
return to local control only if Local Lockout is OFF. If Local
Lockout is ON, the RESET key is ignored.
No parallel poll capability in the 5335A.
When a universal or selected device clear is received, the instru¬
ment clears out ail input buffers and resets the hardware for a
new measurement. The display will flash momentarily. SRQ is
also cleared. Device clear can be used to clear an ERROR
message.
When a device trigger is received,ia new measurement is started.
No controller capability in the 5335A.
3-160. Messages are the means by which devices exchange control and measurement infor¬
mation. There are 12 basic messages which can be sent over the interface. Table 3-4 lists each
bus message, a description of the message, how the 5335A uses that message, and examples of
the various controller’s implementation of the messages.
3-161. Address Selection
3-162. To use the 5335A in an HP-IB system, first set the rear panel address switches as shown in
Table 3~5. The leftmost switch sets the counter to the ADDRESSABLE mode or the TALK ONLY
mode. ADDRESSABLE mode is used whenever a calculator or other controller is used with the
system. TALK ONLY mode is used when the counter is operating under its own control (no con¬
troller on bus) and outputs its measured result to another device on the bus, such as a printer.
3-163. The five righthand switches, As through Ai, set the talk and listen addresses of the
5335A when it is used in the ADDRESSABLE mode. Table 3-5 shows the possible address settings
and the corresponding ASCII codes for talk and listen.
3-164. The examples listed in this section assume an address setting of 00011, which is a 5-bit
binary code for the decimal number three. This number is important when using an HP 9825A,
9835A, or 9845A calculator, since the calculator addresses the 5335A to talk and listen by using the
code 703. (The "03” being the 5335A address.) The ASCII characters for this same switch setting
are “C” for a talk address and "#” for a listen address. These characters are used when the com¬
puting controller is an HP 9830A calculator.
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