PAL20X8 PAL DESIGN SPECIFICATION P7023 (SN54/74LS461) BIRKNER/KAZMI/BLASCO 02/10/81 OCTAL COUNTER MMI SUNNYVALE, CALIFORNIA CLK I0 D0 D1 D2 D3 D4 D5 D6 D7 I1 GND /OC /CO Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 /CI VCC /Q0 := /I1*/I0 ;CLEAR LSB + I0*/Q0 ;COUNT/HOLD :+: I1*/I0*/D0 ;LOAD D0 (LSB) + I1* I0* CI ;COUNT /Q1 := /I1*/I0 ;CLEAR + I0*/Q1 ;COUNT/HOLD :+: I1*/I0*/D1 ;LOAD D1 + I1* I0* CI*Q0 ;COUNT /Q2 := /I1*/I0 ;CLEAR + I0*/Q2 ;COUNT/HOLD :+: I1*/I0*/D2 ;LOAD D2 + I1* I0* CI*Q0*Q1 ;COUNT /Q3 := /I1*/I0 ;CLEAR + I0*/Q3 ;COUNT/HOLD :+: I1*/I0*/D3 ;LOAD D3 + I1* I0* CI*Q0*Q1*Q2 ;COUNT /Q4 := /I1*/I0 ;CLEAR + I0*/Q4 ;COUNT/HOLD :+: I1*/I0*/D4 ;LOAD D4 + I1* I0* CI*Q0*Q1*Q2*Q3 ;COUNT /Q5 := /I1*/I0 ;CLEAR + I0*/Q5 ;COUNT/HOLD :+: I1*/I0*/D5 ;LOAD D5 + I1* I0* CI*Q0*Q1*Q2*Q3*Q4 ;COUNT /Q6 := /I1*/I0 ;CLEAR + I0*/Q6 ;COUNT/HOLD :+: I1*/I0*/D6 ;LOAD D6 + I1* I0* CI*Q0*Q1*Q2*Q3*Q4*Q5 ;COUNT /Q7 := /I1*/I0 ;CLEAR MSB + I0*/Q7 ;COUNT/HOLD :+: I1*/I0*/D7 ;LOAD D7 (MSB) + I1* I0* CI*Q0*Q1*Q2*Q3*Q4*Q5*Q6 ;COUNT IF (VCC) CO = CI*Q0*Q1*Q2*Q3*Q4*Q5*Q6*Q7 ;CARRY OUT FUNCTION TABLE CLK /OC I1 I0 D7 D6 D5 D4 D3 D2 D1 D0 /CI /CO Q7 Q6 Q5 Q4 Q3 Q2 Q1 Q0 ; -INPUT-- -OUTPUT- ;CONTROL INSTR DDDDDDDD CARRY QQQQQQQQ COMMENTS ;CLK /OC I1 I0 76543210 /CI /CO 76543210 (HEX VALUES) ------------------------------------------------------------------------------- C L H L LLLLLLLH X H LLLLLLLH LOAD (01) C L H H XXXXXXXX L H LLLLLLHL INCREMENT C L H L LLLLLLHH X H LLLLLLHH LOAD (03) C L H H XXXXXXXX L H LLLLLHLL INCREMENT C L H L LLLLLHHH X H LLLLLHHH LOAD (07) C L H H XXXXXXXX L H LLLLHLLL INCREMENT C L H L LLLLHHHH X H LLLLHHHH LOAD (0F) C L H H XXXXXXXX L H LLLHLLLL INCREMENT C L H L LLLHHHHH X H LLLHHHHH LOAD (1F) C L H H XXXXXXXX L H LLHLLLLL INCREMENT C L H L LLHHHHHH X H LLHHHHHH LOAD (3F) C L H H XXXXXXXX L H LHLLLLLL INCREMENT C L H L LHHHHHHH X H LHHHHHHH LOAD (7F) C L H H XXXXXXXX L H HLLLLLLL INCREMENT C L H L HHHHHHHH L L HHHHHHHH LOAD (FF) C L H H XXXXXXXX L H LLLLLLLL INCREMENT (ROLL OVER) C L H L HHHHHHHH L L HHHHHHHH LOAD (FF) C L H L HHHHHHHL X H HHHHHHHL LOAD (FE) C L H L HHHHHHLH X H HHHHHHLH LOAD (FD) C L H L HHHHHLHH X H HHHHHLHH LOAD (FB) C L H L HHHHLHHH X H HHHHLHHH LOAD (F7) C L H L HHHLHHHH X H HHHLHHHH LOAD (EF) C L H L HHLHHHHH X H HHLHHHHH LOAD (DF) C L H L HLHHHHHH X H HLHHHHHH LOAD (BF) C L H L LHHHHHHH X H LHHHHHHH LOAD (7F) C L H L HHHHHHHH L L HHHHHHHH LOAD (FF) C L L L XXXXXXXX X H LLLLLLLL CLEAR C L H H XXXXXXXX L H LLLLLLLH INCREMENT TO (01) C L H H XXXXXXXX L H LLLLLLHL INCREMENT TO (02) C L H H XXXXXXXX L H LLLLLLHH INCREMENT TO (03) C L H H XXXXXXXX L H LLLLLHLL INCREMENT TO (04) C L H H XXXXXXXX L H LLLLLHLH INCREMENT TO (05) C L H H XXXXXXXX L H LLLLLHHL INCREMENT TO (06) C L H H XXXXXXXX L H LLLLLHHH INCREMENT TO (07) C L H H XXXXXXXX L H LLLLHLLL INCREMENT TO (08) C L H H XXXXXXXX L H LLLLHLLH INCREMENT TO (09) C L H H XXXXXXXX L H LLLLHLHL INCREMENT TO (0A) C L H H XXXXXXXX L H LLLLHLHH INCREMENT TO (0B) C L H H XXXXXXXX L H LLLLHHLL INCREMENT TO (0C) C L H L HHHHHHHL X H HHHHHHHL LOAD (FE) C L H H XXXXXXXX L L HHHHHHHH INCREMENT TO (FF) /CO=L C L H H XXXXXXXX H H HHHHHHHH CI INHIBITS COUNT AND CO C L L H LLLLLLLL L L HHHHHHHH HOLD SEL INHIBITS COUNT ONLY C L H H HHHHHHHH L H LLLLLLLL INCREMENT TO (00) X H X X XXXXXXXX X X ZZZZZZZZ TEST HI-Z ------------------------------------------------------------------------------- DESCRIPTION THIS IS AN 8-BIT SYNCHRONOUS COUNTER WITH PARALLEL LOAD, CLEAR, AND HOLD CAPABILITY. THE LOAD OPERATION LOADS THE INPUTS (D7-D0) INTO THE OUTPUT REGISTER (Q7-Q0). THE CLEAR OPERATION RESETS THE OUTPUT REGISTER TO ALL LOWS. THE HOLD OPERATION HOLDS THE PREVIOUS VALUE REGARDLESS OF CLOCK TRANSITIONS. THE INCREMENT OPERATION ADDS ONE TO THE OUTPUT REGISTER WHEN THE CARRY-IN IS TRUE (/CI=L), OTHERWISE THE OPERATION IS A HOLD. THE CARRY-OUT (/CO) IS TRUE (/CO=L) WHEN THE OUTPUT REGISTER (Q7-Q0) IS ALL HIGHS, OTHERWISE FALSE (/CO=H). THESE OPERATIONS ARE EXERCISED IN THE FUNCTION TABLE AND SUMMARIZED IN THE OPERATIONS TABLE: /OC CLK I1 I0 /CI D7-D0 Q7-Q0 OPERATION -------------------------------------------------- H X X X X X Z HI-Z L C L L X X L CLEAR L C L H X X Q HOLD L C H L X D D LOAD L C H H H X Q HOLD L C H H L X Q PLUS 1 INCREMENT -------------------------------------------------- TWO OR MORE OCTAL COUNTERS MAY BE CASCADED TO PROVIDE LARGER COUNTERS. THE OPERATION CODES WERE CHOSEN SUCH THAT WHEN I1 IS HIGH, I0 MAY BE USED TO SELECT BETWEEN LOAD AND INCREMENT AS IN A PROGRAM COUNTER (JUMP/INCREMENT). ALSO, CARRY-OUT (/CO) AND CARRY-IN (/CI) ARE LOCATED ON PINS 14 AND 23 RESPECTIVELY, WHICH PROVIDES FOR CONVENIENT INTERCONNECTIONS WHEN TWO OR MORE OCTAL COUNTERS ARE CASCADED TO IMPLEMENT LARGER COUNTERS. $