Measurement Computing TempScan/1100 - Manual (Page 94)

5-4 System Operation 889897 TempScan / MultiScan User's Manual
Trigger Overrun
A Trigger overrun (as opposed to a buffer overrun) condition exists if more than one Trigger (trigger start
event) or more than one Stop (trigger stop event) occurs during one Trigger Block acquisition. This
condition is flagged and notification is given, but no other action is taken. The Trigger Overrun Bit (Bit 4)
in the Error Source Register (
ESC
) is set. You may query the
ESC
via the Query Error Status (
E?
)
command to determine if a Trigger overrun has occurred.
Buffer Query Operation
The Acquisition Buffer holds scan data that has been initiated by one or more Triggers (trigger start events),
where each Trigger Block defines one acquisition and thus contains one and only one Trigger (trigger start
event). These Trigger Blocks may also be variable in length.
The current status of the Acquisition Buffer may be interrogated at any time by issuing the following User
Status (
U
) command query – Query the Buffer Status String (
U6
). As mentioned earlier, the
U6
command is
a user query command which provides the interface in which the current Acquisition Buffer configuration
may be queried, and which returns information regarding the current state of the Acquisition Buffer when
issued.
The Query the Buffer Status String (
U6
) command returns the following fields:
• Number of Trigger Blocks Available (Field 1). Format:
xxxxxxx
. This field represents the total
number of Trigger Blocks currently contained within the Acquisition Buffer, at the time the
U6
command was issued. The number of completed Trigger Blocks is not counted, but rather the number
of detected Triggers is counted. If their are no Trigger Blocks available, then this field will have the
value
0000000
.
• Number of Scans Available (Field 2). Format:
xxxxxxx
. This field represents the total number of
scans available across all Trigger Blocks in the Acquisition Buffer, at the time the
U6
command was
issued. It should be noted that Pre-Trigger data is not available to you until the defined Trigger has
occurred. If their are no scans available in the buffer, then this field will have the value
0000000
.
• Current Position of Read Pointer (Field 3). Format: ±±±±xxxxxxx . This field represents the current read
location within the currently-read Trigger Block. This Read Pointer is relative to the Trigger scan
point, which is always oriented at logical scan location 0. If the Trigger scan is currently being read,
then the Read Pointer will have the value
0000000
. If Pre-Trigger scans are currently being read, the
Read Pointer will have a negative integer value. Likewise, if Post-Trigger scans are currently being
read, the Read Pointer will have a positive integer value. If the Read Pointer is undefined at the time
the
U6
command was issued, then its value will be
-0999999
.
• Time/Date Stamping of Trigger Event (Field 4). Absolute ASCII format:
hh:mm:ss.mil,MM/DD/YY
. Relative ASCII format:
+hh:mm:ss.mil,DDDDDDD
. Absolute Binary
format:
hmstuvwMDY
. Absolute Binary format:
hmstuvwDEF
. This field represents the absolute or
relative Time/Date value when the Trigger event occurred for the currently-read Trigger Block. If the
Trigger event has not yet occurred at the time the
U6
command was issued, then this field will have the
following value:
• Absolute ASCII value
00:00:00.00,00/00/00
,
• Relative ASCII value
+00:00:00.00,0000000
,
• Absolute Binary value
00 00 00 00000000 00 00 00
(2-2-2-8-2-2-2 digits), or
• Relative Binary value:
00 00 00 00000000 000000
(2-2-2-8-6 digits).
• Position of Stop Event Pointer (Field 5). Format: ±±±±xxxxxxx . This field represents the Stop event
location within the currently-read Trigger Block. This Read Pointer is relative to the Trigger scan
point, which is always oriented at logical scan location 0. Since the Stop event must always occur after
the Trigger event, this Read Pointer will always have a positive integer value. If the Stop event has not
yet occurred at the time the
U6
command was issued, this field will have the undefined value
-
0999999
.