Polling HP-IB Devices
Parallel Poll is the fastest means of gathering device status when several
devices are connected to the bus. Each device (with this capability) can
be programmed to respond with one bit of status when parallel polled.
This makes it possible to obtain the status of several devices in one
operation. If a device responds affirmatively to a parallel poll, more
information about its specific status can be obtained by conducting a serial
poll of the device.
Configuring Parallel
Certain devices, including the HP 1650B/1651B, can be remotely
Poll Responses
programmed by a controller to respond to a parallel poll. A device which
is currently configured for a parallel poll responds to the poll by placing
its current status on one of the bus data lines. The response and the
data-bit number can then be programmed by the PPC (parallel Poll
Configure) statement. No multiple listeners can be specified in this
statement. If more than one device is to respond on a single bit, each
device must be configured with a separate PPC statement.
Example:
ASSIGN @Device TO 707
PPOLL CONFIGURE
@Device;Mask
The value of Mask (any numeric expression can be specified) is first
rounded and then used to configure the device’s parallel response. The
least significant 3 bits (bits 0 through 2) of the expression are used to
determine which data line the device is to respond on (place its status on).
Bit 3 specifies the “true” state of the parallel poIl response bit of the
device. A value of 0 implies that the device’s response is 0 when its status
bit message is true.
Example:
The following statement configures the device at address 07 on the
interface select code 7 to respond by placing a 0 on bit 4 when its status
response is “true.”
PPOLL CONFIGURE
707;4
Status Reporting
B-10
HP 1650B/HP 16518
Programming Reference
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