NIHSDIO_ATTR_FETCH_RELATIVE_TO
Specific Attribute
| Data type |
Access | Applies to | Coercion | High-Level Functions |
|---|---|---|---|---|
| ViInt32 | R/W | N/A | None | None |
Description
Specifies the absolute location within the acquired record from which to begin fetching. The default value is NIHSDIO_VAL_CURRENT_READ_POSITION. If the Reference trigger is enabled, the read position is initially set to the first pretrigger sample. If the Reference trigger is disabled, the read position is initially set to the first sample acquired. After every fetch, the read position moves to the sample immediately after the last fetched sample. Thus, if you call fetch multiple times and NIHSDIO_ATTR_FETCH_RELATIVE_TO is set to NIHSDIO_VAL_CURRENT_READ_POSITION, each fetch retrieves a different part of the record. If NIHSDIO_ATTR_FETCH_RELATIVE_TO is set to any other value, you must modify NIHSDIO_ATTR_FETCH_OFFSET between fetches to fetch different parts of the record.
Defined Values:
| NIHSDIO_VAL_MOST_RECENT_SAMPLE (46) | Specifies that fetching occur relative to the most recently acquired data. The fetch offset (NIHSDIO_ATTR_FETCH_OFFSET) must be negative. |
| NIHSDIO_VAL_FIRST_SAMPLE (47) | Specifies that fetching occurs at the first sample acquired by the device. If the device wraps its buffer, then the first sample is no longer available. In this case, NI-HSDIO returns an error if the fetch offset is in the overwritten data. |
| NIHSDIO_VAL_REFERENCE_TRIGGER (48) | Specifies that fetching occur relative to the Reference trigger. This value behaves like NIHSDIO_VAL_FIRST_SAMPLE if no Reference trigger is configured. |
| NIHSDIO_VAL_FIRST_PRETRIGGER_SAMPLE (49) | Specifies that fetching occur relative to the first pretrigger sample acquired. This value behaves like NIHSDIO_VAL_FIRST_SAMPLE if no Reference trigger is configured. |
| NIHSDIO_VAL_CURRENT_READ_POSITION (50) | Specifies that fetching occur after the last fetched sample. |