Yokogawa Button Operated MV2000 - Manual (Page 172)

App-8 M-4662
Appendix 5 Flowchart of the FIFO Data Output
FIFO Buffer Overview
The MV has an exclusive internal memory for transmitting measured/computed data. The
memory has a FIFO (First-In-First-Out) structure. Measured/computed data is constantly
acquired to the internal memory at the specified acquisition interval (FIFO acquisition
interval, set with the FR command). By using this function, you will be able to read
measured/computed data that has been saved at the specified interval, independent of
when the PC reads the measured/computed data.
The following example shows the case when the acquisition interval is 1 s, and the
FIFO memory can store data 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
• Measured/Computed Data Acquisition
• The MV acquires measured/computed data to the internal memory at 1-s intervals.
• The MV acquires measured/computed data in order to positions 1 through 8. After
acquiring to position 8, the MV acquires the next data to position 1.
• Reading the Measured/Computed Data (using the FF GET command)
The MV transmits the data from the previous read position (RP1) to the most recent
acquisition position (WP).
In this example, more than 2 seconds has elapsed from the previous read operation.
Therefore, the MV transmits the data from blocks 5 and 6.
The amount of internal memory allocated for the FIFO buffer (FIFO buffer data size)
varies depending on the model.
Model Data size
RD-MV1004, RD-MV1008, RD-MV2008 For 1200 intervals (30 s at the fastest acquisition
interval of 25 ms)
RD-MV1006, RD-MV1012, RD-MV1024,
RD-MV2010, RD-MV2020, RD-MV2030,
RD-MV2040, RD-MV2048 For 240 intervals (30 s at the fastest acquisition
interval of 125 ms)
Models with the external channel input
option For 60 intervals (60 s at the fastest acquisition interval
of 1 s)