SECTION 2. INTERNAL DATA STORAGE

2.1FINAL STORAGE AREAS, OUTPUT ARRAYS, AND MEMORY POINTERS

Final Storage is that portion of memory where final processed data are stored. It is from Final Storage that data is transferred to your computer or external storage peripheral.

The size of Final Storage is expressed in terms of memory locations or bytes. A low resolution data point (4 decimal characters) occupies one memory location (2 bytes), whereas a high resolution data point (5 decimal characters) requires two memory locations (4 bytes). Table 1.5-1 shows the default allocation of memory locations to Input, Intermediate, and the two Final Storage areas. The *A Mode is used to reallocate memory or erase Final Storage (Section 1.5).

The default size of Final Storage is 64K bytes or 29908 low resolution memory locations. One RAM chip is dedicated to Final Storage. This chip has 32K bytes. A minimum of 32K bytes (16K memory locations) is ALWAYS retained in Final Storage.

Final Storage can be divided into two parts: Final Storage Area 1 and Final Storage Area 2.

Final Storage Area 1 is the default storage area and the only one used if the operator does not specifically allocate memory to Area 2. A minimum of 768 memory locations will ALWAYS be retained in Final Storage Area 1.

Two Final Storage Areas may be used to:

1.Output different data to different devices.

2.Separate archive data from real time display data. In other words, you can record a short time history of real time data and separately record long term, archive data.

3.Record both high speed data (fast recording interval) and slow data without having the high speed data write over the slow data.

Each Final Storage Area can be represented as ring memory (Figure 2.1-1) on which the newest data are written over the oldest data.

The Data Storage Pointer (DSP) is used to determine where to store each new data point in the Final Storage area. The DSP advances to the next available memory location after each new data point is stored.

FIGURE 2.1-1. Ring Memory Representation of Final Data Storage

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