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71 lines
3.0 KiB
Plaintext
71 lines
3.0 KiB
Plaintext
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Bit Manipulation Functions for C02 Programs
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This module contains functions to shift and rotate the bits in a byte,
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and to extract, combine, swap and duplicate nybbles in a byte.
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At the beginning of the program use the directives
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#include <stddef.h02>
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#include <bitlib.h02>
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The following functions are defined:
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r = shiftl(b,n) Shifts byte b by n bits to the left and returns
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the result in r. If n is 0, the byte is not
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shifted, and if n greater than 8, the returned
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value will be 0.
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r = shiftr(b,n) Shifts byte b by n bits to the right and returns
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the result in r. If n is 0, the byte is not
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shifted, and if n greater than 8, the returned
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value will be 0.
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r = rotl(b,n) Rotate byte b by n bits to the left and returns
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the result in r, with the high bit rotated into
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the low bit on each rotation. If n is 0, the
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byte is not rotated, and any value of n greater
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than 8, will return the same result as n modulo 8.
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r = rotr(b,n) Rotate byte b by n bits to the right and returns
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the result in r, with the high bit rotated into
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the low bit on each rotation. If n is 0, the
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byte is not rotated, and any value of n greater
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than 8, will return the same result as n modulo 8.
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b = pack(l,r); Packs the low nybbles of bytes l and r into a
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single byte, with l becoming the left (or high)
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nybble and r becoming the right (or low) nybble.
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and returns the packed byte in b.
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l,r = unpack(b); Unpacks byte b, returning the left (or high)
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nybble in l, and the right (or low) nybble in r.
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d = dupl(b); Duplicates the low nybble of byte b into the
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high nybble and returns the new byte in d.
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Note: Executes function pack() with b as both
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arguments.
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d = swap(b); Swaps the left (or high) and right (or low)
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nybbles of byte b and returns the new byte in d.
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Note: Executes function rotl() with the arguments
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b and 4.
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c,d,e = func(a,&d); Stores the input value a and the address of d
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in memory.
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Returns three bytes read from memory.
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Note: Writes argument a to variable arg0,
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the address of d to variables adr0 and adr1,
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and returns the values of variables var0,
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var1, and var2.
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Note: This library expects the following external variables to be defined:
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temp0: Temporary Variable
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