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Teledyne LeCroy Protocol Analyzers File-Based Decoding User Manual User Manual

Page 46

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Chapter 11: Primitives

File-based Decoding User Manual

40

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.