A source value of 8 is consistent with bit 3 being set when GetBit uses zero-based bit numbering. A channel configured to read bit 4 should return 0, while incorrect Integer conversion on the bit 3 channel can produce an invalid or unreadable display.
Interpret the Source Value
Bit positions start at 0. Decimal 8 has only bit 3 set:
8 decimal = 1000 binary
bit 4 = 0
bit 3 = 1This explains why GetBit returns 0 for bit 4 and should return 1 for bit 3. Here, 3 and 4 are interpreted as bit indexes; if they are device register addresses instead, the available evidence is insufficient to diagnose the result.
Correct the Channel Data Type
Do not convert the GetBit channel to Integer while diagnosing the malformed value. Leave the data type as Double or blank. The evidence associates the unreadable bit 3 result with Integer conversion, although that behavior was not independently verified.
Set the Display Format
Configure the channel display format as D. This displays the extracted bit as a decimal value and avoids presenting its underlying representation as an unintended format.
Apply and Verify the Configuration
- Confirm that the channel input is the source value 8.
- Configure GetBit with bit index 3.
- Set the format to
D. - Set the data type to Double or leave it blank instead of selecting Integer.
- Verify that bit 3 displays 1 and bit 4 displays 0 while the source remains 8.
If bit 3 still displays malformed data, compare the complete channel settings for the working bit 4 channel and the failing bit 3 channel. Focus on GetBit selection, data type, and display format.
FAQ
Why does Rapid SCADA GetBit return 1 for bit 3 when the value is 8?
GetBit uses zero-based indexing in this case. Decimal 8 is binary 1000, so bit 3 is 1.
Why does GetBit return 0 for bit 4 with a source value of 8?
Decimal 8 does not have bit 4 set. With zero-based numbering, bit 4 therefore returns 0.
How do I fix a malformed Rapid SCADA GetBit value?
Set the channel format to D and avoid Integer conversion. Leave the data type as Double or blank, then verify that bit 3 reads 1 and bit 4 reads 0 for source value 8.