IOtech MultiScan 1200, Руководство пользователя

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TempScan / MultiScan User's Manual Chapter 13: System Operation 201
This field will always have the same value as the Position of Stop Event Pointer field unless Post-
Stop scans have been configured; that is, if the Post-Stop
stop
parameter of the Set Counts (
Y
)
command has been set to a non-zero value. In this case, this Position of End Scan Pointer field
will have a greater value than the Position of Stop Event Pointer field.
•
Status of Current Trigger Block (Field 8). Format:
xx
. This field represents the status of the
currently-read Trigger Block . If the currently-read Trigger Block is still being acquired, then this
field will have the value
00
. If the currently-read Trigger Block has been completely acquired and
has terminated normally, then this field will have the value
01
. However, if the currently-read
Trigger Block has prematurely terminated (due to user intervention), then this field will have the
value
02
.
It should be noted that Trigger Blocks are not assigned a Trigger Block number as such. These Trigger
Block numbers refer to locations relative to the currently-read Trigger Block . Consequently, the
Trigger Block currently being read is always Trigger Block 1. Meanwhile, the Trigger Block currently
being written is always the value of the Number of Trigger Blocks Available field.
Buffer Read Operations
As mentioned earlier, the TempScan/1100 or MultiScan/1200 Acquisition Buffer is a FIFO (First-In
First-Out) buffer. In other words, the oldest scan data to be written into the buffer is the first scan data
to be read from the buffer when a read operation is performed. Then once the scan data is read from
the buffer by the controller, that data is erased from the buffer.
The Acquisition Buffer data is read via the Read Buffered Data (
R
) command. You can use this
command to read anywhere from one scan to all the scan data currently residing in the buffer. This
command has the following valid options:
•
Read the oldest scan currently residing in the Acquisition Buffer (
R1
).
•
Read the oldest complete Trigger Block currently residing in the Acquisition Buffer (
R2
).
•
Read all the scan data currently residing in the Acquisition Buffer (
R3
).
When a Read Buffered Data (
R
) command is issued, the TempScan/1100 or MultiScan/1200 checks to
see if the read request can be fulfilled. If so, the requested scan data is moved from the Acquisition
Buffer to the Output Queue where it waits until the controller initiates transfer. However, if either of
the following is true – No channels are configured, or the amount of scan data requested is not
available – then the read request will not be fulfilled, and a
Conflict Error will be posted. The
R1
and
R3
commands require that at least one scan be available, and the
R2
command requires that at least one
complete Trigger Block be available.
The Scan Available Bit (Bit 3) in the Status Byte Register (
STB
) can be used to determine whether or
not the Acquisition Buffer is empty. This bit is set when at least one scan is available in the buffer.
The following
User Status (
U
) command query – Query the Buffer Status String (
U6
) – may also be
used to retrieve more-detailed information about the state of the Acquisition Buffer.
Note: The responses to all queries (including
U6
,
R1
, and
R2
) can be configured with specific field
separators and response terminators. For details on setting query terminators, see command
Set Query Terminator (
Q
) in the chapter API Command Reference .