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; Copyright 2014, Sinclair R.F., Inc.
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; Copyright 2014, Sinclair R.F., Inc.
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;
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;
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; Unsigned arithmetic operations.
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; Unsigned arithmetic operations.
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; Notation:
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; ux_n is the n'th byte of ux where n=0 is the LSB
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; example: ( u0_0 u0_1 ) are the LSB and MSB of a 2-byte 16-bit value.
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; u0 and u1 are two input vectors, us is their sum
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;
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;
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; Add two unsigned 8-bit values to produce an unsigned 16-bit value.
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; Add two unsigned 8-bit values to produce an unsigned 16-bit value.
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; Method: Calculate the sum of the msb of the two raw values and the msb of the
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; Method: calculate and push the carry bit onto the return stack, calculate the
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; sums of the 7 lsbs of the two values to get the msb of the sum and
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; 8-bit sum of the two 8-bit values, use the previously stored and
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; the lsb of the MSB of the 16-bit sum.
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; computed carry bit as the MSB of the 16-bit return value.
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; 36 instructions
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; 6 instructions
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;
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;
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; ( u1 u2 - (u1+u2)_LSB (u1+u2)_MSB )
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; ( u0 u1 - us_0 us_1 )
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.function math__add_u8_u8_u16
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.function math__add_u8_u8_u16
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; and the two 7 lsbs and put the 7 lsb of that sum on the return stack
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; ( u_0 u_1 - u_0 u_1 ) r:( - c )
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over 0x7F & over 0x7F & + dup 0x7F & >r
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; ( u0 u1 - us_0 us_1 )
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; add the msb of the sum of the 7 lsbs and the two inputs
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+c >r + r>
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0x80 & <<msb swap 0x80 & <<msb + swap 0x80 & <<msb +
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.return
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; construct the MSB of the sum as bit 1 of the sums of the msbs
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dup 0>> swap
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; set the msb of the LSB if the lsb of the sum of the msbs is non-zero
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0x01 & 0<> 0x80 & r> or
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; swap the orders so that the MSB is on the top of the data stack
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.return(swap)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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; miscellaneous unsigned addition operations
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; miscellaneous unsigned addition operations
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; ( u0_0 u0_1 u0 - us_0 us_1 )
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; 9 instructions
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.function math__add_u16_u8_u16
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.function math__add_u16_u8_u16
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swap >r .call(math__add_u8_u8_u16) r> .return(+)
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; ( u0_0 u0_1 u1 - u0_0 u1 ) r:( - u0_1 )
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swap >r
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; ( u0_0 u1 - us_0 c_0 )
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+c >r + r>
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; ( c_0 - us_1 ) r:( u0_1 )
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r> .return(+)
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; ( u0_0 u0_1 u1 - us_0 us_1 us_2 )
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; 13 instructions
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.function math__add_u16_u8_u24
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.function math__add_u16_u8_u24
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swap >r .call(math__add_u8_u8_u16) r> .call(math__add_u8_u8_u16) .return
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; ( u0_0 u0_1 u1 - u0_0 u1 ) r:( - u0_1 )
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swap >r
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; ( u0_0 u1 - us_0 c_0 )
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+c >r + r>
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; ( c_0 - us_1 us_2 ) r:( u0_1 - )
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r> +c >r + r>
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.return
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; ( u0_0 u0_1 u0_2 u1 - us_0 us_1 us_2 )
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.function math__add_u24_u8_u24
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.function math__add_u24_u8_u24
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swap >r .call(math__add_u16_u8_u24)
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swap >r .call(math__add_u16_u8_u24)
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r> .return(+)
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r> .return(+)
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; ( u0_0 u0_1 u0_2 u1 - us_0 us_1 us_2 us_3 )
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.function math__add_u24_u8_u32
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.function math__add_u24_u8_u32
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swap >r .call(math__add_u16_u8_u24)
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swap >r .call(math__add_u16_u8_u24)
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r> .call(math__add_u8_u8_u16)
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r> .call(math__add_u8_u8_u16)
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.return
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.return
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