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1995-04-05
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935b
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35 lines
CHIP add IFX780_84
PIN a[0:7] ; 8-bit a input
PIN b[0:7] ; 8-bit b input
PIN sum[0:7] ; 8-bit sum of a+b
PIN cry[1:7] ; 7 bits of carry info
PIN 47 clk ; shift-reg clock
PIN 48 shift ; shift-reg enable
PIN 49 in ; shift-reg input
PIN 50 unused1 ; unused pins that are
PIN 51 unused2 ; connected to the PC
PIN 77 unused3 ; printer port so we
PIN 78 unused4 ; make sure they are
; not used elsewhere
EQUATIONS
; this builds two concatenated 8-bit
; shift registers which shift only
; when shift is high
a0 := in
a[7:1] := a[6:0]
b0 := a7
b[7:1] := b[6:0]
a[7:0].ACLK = clk * shift
b[7:0].ACLK = clk * shift
; these are the equations for an 8-bit
; ripple-carry adder
sum0 = a0 :+: b0
sum[7:1] = a[7:1] :+: b[7:1] :+: cry[7:1]
cry1 = a0 * b0
cry[7:2] = a[6:1] * b[6:1] +
a[6:1] * cry[6:1] +
b[6:1] * cry[6:1]