Measurement Computing TempScan/1100 - Manual (Page 91)

TempScan / MultiScan User's Manual 889897 System Operation 5-1
System Operation 5
Acquisition Buffer …… 5-1
Buffer Organization …… 5-2
Buffer Query Operation …… 5-4
Buffer Read Operations …… 5-5
Buffer Overrun …… 5-11
High/Low/Last (HLL) Registers …… 5-13
Contents of the HLL Registers …… 5-13
Access to the HLL Registers …… 5-14
Comparing Buffered Data to HLL Data …… 5-17
Status-Reporting & Mask Registers …… 5-18
Theory of Operation …… 5-19
Status-Reporting Registers …… 5-19
Mask Registers …… 5-23
Using Status-Reporting Registers …… 5-24
Additional Operation …… 5-25
Trigger Latency …… 5-25
Real-Time Clock …… 5-26
Open Thermocouple & Range Error Checking …… 5-26
Software Digital Filtering (TempScan/1100 Only) …… 5-26
Acquisition Buffer
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 buffer may consist of one or more Trigger Blocks. In turn, a Trigger Block can consist of the following
components as discussed in the previous chapter: Pre-Trigger scans (optional), Post-Trigger scans
(required), and Post-Stop scans (optional). These components constitute a single Trigger Block in the
internal memory of the TempScan/1100 or MultiScan/1200 unit. Each Trigger Block defines an acquisition
and thus contains one and only one Trigger (trigger start event). These Trigger Blocks may also be variable
in length.
Multiple Trigger Blocks are allocated sequentially, and the scans within each Trigger Block are written and
read sequentially. It is not possible to randomly access a Trigger Block or a scan within a Trigger Block.
When a read operation is performed, the scan that is read is the oldest scan in the oldest trigger block
currently defined.