IOtech MultiScan 1200, User Manual

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TempScan / MultiScan User's Manual Chapter 13: System Operation 219
Status Byte Register (STB)
The Status Byte Register (
STB
) is a Read-Only register in that it can only be read by the controller, via
the Serial Poll (
SPOLL
) command (IEEE 488 only) or the following User Status (
U
) command – Query
the Status Byte Register (
U1
) (IEEE 488 or serial). This register can only be cleared or written to by
the internal processes of the TempScan/1100 or MultiScan/1200.
The Status Byte Register (
STB
) is at the lowest-level status-reporting register in the register hierarchy.
When the controller accesses this register in real-time via an IEEE 488
SPOLL
command, this access
allows the quick response of certain critical operational status conditions contained in the
STB
. Since
this is the lowest-level register, every other status register in the system, either directly or indirectly, has
access to the
STB
via the Event Status Register Bit (
ESR
Bit 5, or
ESB
) in the
STB
. Such access gives
these other status registers the ability to quickly report their general status to the controller.
The TempScan/1100 or MultiScan/1200 sets the Message Available Bit (
MAV
,Bit 4) in the Status Byte
Register (
STB
) to determine if data can be read by the controller. This is the only status register which
may require the RS-232/RS-422 serial interface to implement a different read command – Query the
Status Byte Register (
U1
) – than the IEEE 488 interface which primarily implements the Serial Poll
(
SPOLL
) command (but can also use the
U1
command).
The Status Byte Register (
STB
) indicates which critical operation events, if any, have occurred. Its bits
and the events that set them, are as follows:
• Buffer Overrun (Bit 7): Set if an overrun of the Acquisition Buffer occurs. It is cleared when the
buffer becomes empty by either reading out the contents of the buffer or performing the Flush
Acquisition Buffer (
*B
) command.
•
Request for Service Bit (RQS) or Master Summary Status Bit (MSS) (Bit 6): Set when the
TempScan/1100 or MultiScan/1200 unit is requesting service. It is cleared when the following is
performed: Serial Poll (
SPOLL
) command (IEEE 488 only) or the following User Status (
U
)
command – Query the Status Byte Register (
U1
) (IEEE 488 or RS-232/RS-422 serial).
•
Event Status Register Bit (ESB) (Bit 5): Reflects the logical OR of all the bits in the Event Status
Register (
ESR
) AND ed with their equivalent enable bits in the Event Status Enable Register (
ESE
).
This bit is set if at least one bit in the
ESR
is set and its corresponding bit in the
ESE
is also set.
•
Message Available (MAV) (Bit 4): Set when there is data available in the output queue to be read.
It is cleared when the output queue is empty. This bit reflects whether any command responses are
still in the output queue.
•
Scan Available (Bit 3): Set when at least one acquisition scan is available in the Acquisition
Buffer to be read. This bit is cleared when there are no scans available in the buffer to be read.
•
Ready (Bit 2): Set when the TempScan/1100 or MultiScan/1200 unit has completed executing a
set of commands and is ready to process another command from the IEEE 488 bus controller. It is
cleared when the unit is processing a command line. This bit should be examined with a Serial
Poll (
SPOLL
) prior to issuing a new command line. This allows any detected errors to be traced to
the specific command line containing the error. If all of the setup information for a specific
operation is included in one line, this bit also indicates when all processing is done and the
Execute
(
X
) command is completed. This ensures that the unit is finished processing all of its internal state
changes before initiating any further activity.
•
Triggered (Bit 1): Set when the TempScan/1100 or MultiScan/1200 unit has detected a valid
Trigger (trigger start event) or Stop (trigger stop event) condition from the programmed trigger
source. This bit is cleared when the acquisition is complete or the Trigger or Stop is reconfigured.
•
Alarm (Bit 0): Set when the TempScan/1100 or MultiScan/1200 unit has detected a valid alarm
condition. This bit is cleared whenever the alarm condition no longer exists.
For more information, see command User Status (
U
) in the chapter API Command Reference .