Teledyne LeCroy Protocol Analyzers File-Based Decoding User Manual - Manual (Page 46)

Chapter 11: Primitives File-based Decoding User Manual
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LeCroy Corporation
GetNBits()
GetNBits (list or raw>, 
integer>, integer>)
Parameter Meaning
Default
Value Comments
bit_source list, raw,
or integer Can be an integer value (4 bytes) or a list of
integers that are interpreted as bytes.
bit_offset integer Index of bit to start
reading from
bit_count integer Number of bits to
read
Support
Supported by all LeCroy analyzers.
Return value
None.
Comments
Reads bit_count bits from bit_source starting at bit_offset. Returns null if
bit_offset + bit_count exceeds the number of bits in bit_source. If bit_count
is 32 or less, the result is returned as an integer. Otherwise, the result is returned in a list
format that is the same as the input format. GetNBits also sets up the bit data source
and global bit offset used by NextNBits and PeekNBits. Note that bits are indexed
starting at bit 0.
Example
raw = 'F0F0'; # 1111000011110000 binary
result = GetNBits ( raw, 2, 4 );
The return value is given in hexadecimal, so in binary it is 1100.The function returns:
C
A call to GetNBits, starting at bit 2, reads 4 bits (1100), and returns the value 0xC.