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INCRMNTR.PDS
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1994-10-05
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;*-- beginning of the incrementer module -----------------
; This is a module which increments its 3-bit input.
; It also has a reset input which forces all its outputs
; to zero.
;---------------------------------------------------------
DEFMOD incrmntr( rst, cur[0:2], nxt[0:2] )
CHIP incrmntr Intel_arch
PIN rst ;* reset counter to 0 (input)
PIN cur[0:2] ;* current counter value (input)
PIN nxt[0:2] ;* next counter value (output)
; the 3-bit incrementer is specified using the following
; truth table. note the first entry which says that the
; output will be all zeroes if the rst input is high
; regardless of what values the other inputs have (don't
; cares are signified by an "x").
T_TAB( rst cur2 cur1 cur0 >> nxt2 nxt1 nxt0 )
1 x x x : 0 0 0 ;* reset to 0
0 0 0 0 : 0 0 1 ;* 0 -> 1
0 0 0 1 : 0 1 0 ;* 1 -> 2
0 0 1 0 : 0 1 1 ;* 2 -> 3
0 0 1 1 : 1 0 0 ;* 3 -> 4
0 1 0 0 : 1 0 1 ;* 4 -> 5
0 1 0 1 : 1 1 0 ;* 5 -> 6
0 1 1 0 : 1 1 1 ;* 6 -> 7
0 1 1 1 : 0 0 0 ;* 7 -> 0
ENDMOD
;*-- end of the incrementer module ----------------------