Yokogawa Removable Chassis DX1000N - Manual (Page 256)

App-9
IM 04L41B01-17E
Appendix
1
2
3
4
5
6
App
Index
Appendix 5 Flow Chart of the FIFO Data Output
Overview of the FIFO Buffer
The DX has a dedicated internal memory for outputting measured/computed data. This
memory is structured as a FIFO (First-In-First-Out). Measured/computed data are
constantly acquired to the internal memory at the specified acquiring interval (FIFO
acquiring interval, set with the FR command). By using this function, it is possible to read
measured/computed data that have been saved at the specified intervals regardless of
the frequency at which the PC periodically reads the measured/computed data.
The following example shows the case when the acquisition interval is 1 s and the
capacity of the FIFO memory is for 8 intervals.
Most recent acquire
Position: WP
Previous read
Position: RP1
Current read
Position: RP2
Block 1
2
3
4
5
6
7
Block 8
• Acquiring of the Measured/Computed Data
• The measured/computed data are acquired to the internal memory at 1 s intervals.
• Measured/computed data is acquired to positions 1 through 8 in order. After
acquiring to position 8, the next data is acquired to position 1.
• Reading the Measured/Computed Data (FF GET command is used)
Outputs the data from the previous read position (RP1) to the most recent acquisition
position (WP).
In this example, more than 2 s has elapsed from the previous read operation.
Therefore, data in blocks 5 and 6 are output.
The size of the internal memory reserved for FIFO (FIFO buffer data size) varies
depending on the model.
Model Data size
DX1002, DX1004, DX2004, and DX2008 1200 intervals (30 s at the fastest acquisition interval
of 25 ms)
DX1006, DX1012, DX2010, DX2020,
DX2030, DX2040, and DX2048
240 intervals (30 s at the fastest acquisition interval of
125 ms)
Models with the external channel input
option
60 intervals (60 s at the fastest acquisition interval of
1 s)