Message Concepts - HP 1630A Operating And Programming Manual

An HP-IB Overview
Model 1630A/D/G
A typical HP-113 system is shown below.
9872-A-172-1
MESSAGE CONCEPTS
Devices which communicate along the interface bus are transferring quantities of information . The transfer of
information can be from one device to another device, or from one device to more than one device . These
quantities of information can easily be thought of as "messages" .
In turn, the messages can be classified into twelve types. The list below gives the twelve message types for the HP-I B.
B- 2
1 . The Data Message -This in the actual information which is sent from one talkerto one or more listeners
along the interface bus.
2. The Trigger Message - This message causes the listening device(s) to perform a device-dependent
action when addressed.
3. The Clear Message - This message causes either the listening device(s) or all of the devices on the bus
to return to their predefined device-dependent states .
4. The Remote Message - This message causes listening devices to switch from local front-panel to
remote program control when addressed to listen .
5 . The Local Message - This message clears the Remote Message from the listening device(s) and
returns the device(s) to local front-panel control .
6 . The Local Lockout Message - This message prevents a device operator from manually inhibiting
remote program control.
7. 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 .
8. The Require Service Message - 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.
9. 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 operational
conditions defined by the device . This byte is sent from a talking device in response to a serial poll
operation performed by a controller .