HP 7470A Interfacing And Programming Manual page 191
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Also See for 7470A:
- Operator's manual (41 pages) ,
- Interfacing and programming manual (114 pages) ,
- Service manual (141 pages)
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10.
11.
12.
. The Remote Message.
. The Require Service Message.
This message causes all devices currently
addressed to listen to switch from local front-panel control to
remote program control.
The Local Message.
This message clears the Remote Message
from the listening device(s) and returns the device(s) to local front
panel control.
The Local Lockout Message. This message prevents a device
operator from manually inhibiting remote program control.
The Clear Lockout/ Local Message. This message causes all
devices on the bus to be removed from Local Lockout and revert to
Local. This message also clears the Remote Message for all devices
on the bus.
A device can send this message
at any time to signify that the device needs some type of interaction
with the controller. This message is cleared by sending the device's
Status Byte Message if the device no longer requires service.
The Status Byte Message. A byte that represents the status of
a single device on the bus. Bit 6 indicates whether the device sent a
Require Service Message, and the remaining bits indicate opera
tional conditions defined by the device. This byte is sent from a
talking device in response to a serial poll operation performed by a
controller.
The Status Bit Message. This byte represents the operational
conditions of a group of devices on the bus. Each device responds
on a particular bit of the byte thus identifying a device—dependent
condition. This bit is typically sent by devices in response to a
parallel poll operation.
The Status Bit Message can also be used by a controller to specify
the particular bit and logic level at which a device will respond
when a parallel poll operation is performed. Thus, more than one
device can respond on the same bit.
The Pass Control Message. This transfers the bus management
responsibilities from the active controller to another controller.
The Abort Message.
The system controller sends this message
to unconditionally assume control of the bus from the active con
troller. This message terminates all bus communications (but does
not implement a Clear Message).
These messages represent the full implementation of all HP—IB system
capabilities. Each device in a system may be designed to use only
the messages that are applicable to its purpose in the system. It is
AN HP-IB OVERVIEW A-3
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