PAL20X10 PAL DESIGN SPECIFICATION P7076 BIRKNER/COLI/LEE 01/12/83 9-BIT DOWN COUNTER MMI SUNNYVALE, CALIFORNIA CLK D0 D1 D2 D3 D4 D5 D6 D7 D8 /LD GND /OC /BO Q8 Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 VCC /Q0 := /LD*/Q0 ;HOLD Q0 + LD*/D0 ;LOAD D0 (LSB) :+: /LD ;COUNT DOWN /Q1 := /LD*/Q1 ;HOLD Q1 + LD*/D1 ;LOAD D1 :+: /LD*/Q0 ;COUNT DOWN /Q2 := /LD*/Q2 ;HOLD Q2 + LD*/D2 ;LOAD D2 :+: /LD*/Q0*/Q1 ;COUNT DOWN /Q3 := /LD*/Q3 ;HOLD Q3 + LD*/D3 ;LOAD D3 :+: /LD*/Q0*/Q1*/Q2 ;COUNT DOWN /Q4 := /LD*/Q4 ;HOLD Q4 + LD*/D4 ;LOAD D4 :+: /LD*/Q0*/Q1*/Q2*/Q3 ;COUNT DOWN /Q5 := /LD*/Q5 ;HOLD Q5 + LD*/D5 ;LOAD D5 :+: /LD*/Q0*/Q1*/Q2*/Q3*/Q4 ;COUNT DOWN /Q6 := /LD*/Q6 ;HOLD Q6 + LD*/D6 ;LOAD D6 :+: /LD*/Q0*/Q1*/Q2*/Q3*/Q4*/Q5 ;COUNT DOWN /Q7 := /LD*/Q7 ;HOLD Q7 + LD*/D7 ;LOAD D7 :+: /LD*/Q0*/Q1*/Q2*/Q3*/Q4*/Q5*/Q6 ;COUNT DOWN /Q8 := /LD*/Q8 ;HOLD Q8 + LD*/D8 ;LOAD D8 (MSB) :+: /LD*/Q0*/Q1*/Q2*/Q3*/Q4*/Q5*/Q6*/Q7 ;COUNT DOWN BO := /LD* Q0*/Q1*/Q2*/Q3*/Q4*/Q5*/Q6*/Q7*/Q8 ;CARRY OUT (ANTICIPATE COUNT) + LD*/D0*/D1*/D2*/D3*/D4*/D5*/D6*/D7*/D8 ;CARRY OUT (ANTICIPATE LOAD) FUNCTION TABLE CLK /OC /LD D8 D7 D6 D5 D4 D3 D2 D1 D0 /BO Q8 Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 ; DATA IN DATA OUT ; CONTROL DDDDDDDDD QQQQQQQQQ ;CLK /OC /LD 876543210 /BO 876543210 COMMENT ------------------------------------------------------------------ C L L LLLLLLLLL L LLLLLLLLL LOAD (BORROW) C L H XXXXXXXXX H HHHHHHHHH DECREMENT C L L LLLLLLLLH H LLLLLLLLH LOAD C L H XXXXXXXXX L LLLLLLLLL DECREMENT (BORROW) C L L LLLLLLLHH H LLLLLLLHH LOAD C L H XXXXXXXXX H LLLLLLLHL DECREMENT C L L LLLLLLHHH H LLLLLLHHH LOAD C L H XXXXXXXXX H LLLLLLHHL DECREMENT C L L LLLLLHHHH H LLLLLHHHH LOAD C L H XXXXXXXXX H LLLLLHHHL DECREMENT C L L LLLLHHHHH H LLLLHHHHH LOAD C L H XXXXXXXXX H LLLLHHHHL DECREMENT C L L LLLHHHHHH H LLLHHHHHH LOAD C L H XXXXXXXXX H LLLHHHHHL DECREMENT C L L LLHHHHHHH H LLHHHHHHH LOAD C L H XXXXXXXXX H LLHHHHHHL DECREMENT C L L LHHHHHHHH H LHHHHHHHH LOAD C L H XXXXXXXXX H LHHHHHHHL DECREMENT C L L HHHHHHHHH H HHHHHHHHH LOAD C L H XXXXXXXXX H HHHHHHHHL DECREMENT C L L HHHHHHHLL H HHHHHHHLL LOAD C L H XXXXXXXXX H HHHHHHLHH DECREMENT L L H XXXXXXXXX H HHHHHHLHH HOLD C L H XXXXXXXXX H HHHHHHLHL DECREMENT C L H XXXXXXXXX H HHHHHHLLH DECREMENT C L H XXXXXXXXX H HHHHHHLLL DECREMENT X H X XXXXXXXXX Z ZZZZZZZZZ TEST HI-Z ------------------------------------------------------------------ DESCRIPTION THE 9-BIT SYNCHRONOUS COUNTER HAS PARALLEL LOAD, DECREMENT, AND HOLD CAPABILITIES. DATA (D8-D0) IS LOADED INTO THE OUTPUT REGISTER (Q8-Q0) WHEN THE LOAD INPUT IS TRUE (/LD=L) AND A POSITIVE EDGE PULSE IS RECEIVED ON THE CLOCK PIN (CLK). THE COUNTER WILL DECREMENT IF A CLOCK PULSE IS RECEIVED WITH THE LOAD INPUT BEING FALSE (/LD=H). THE OPERATION IS A HOLD IF NO CLOCK PULSE IS RECEIVED REGARDLESS OF ANY OTHER INPUTS. THE BORROW OUT PIN (/BO) SHOWS HOW TO IMPLEMENT A BORROW OUT USING A REGISTER BY ANTICIPATED ONE COUNT BEFORE THE TERMINAL COUNT IF COUNTING AND THE TERMINAL COUNT IF LOADING. OPERATIONS TABLE: /OC CLK /LD D8-D0 Q8-Q0 OPERATION ---------------------------------------------- H X X X Z HI-Z L L X X /Q HOLD L C L D D LOAD L C H X Q MINUS 1 DECREMENT ----------------------------------------------