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Details, datasheet, quote on part number:SN74AS169A
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Datasheet text preview:
SN54ALS169B, SN54AS169A, SN74ALS169B, SN74AS169A SYNCHRONOUS 4-BIT UP/DOWN BINARY COUNTERS
SDAS125B MARCH 1984 REVISED DECEMBER 1994
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Fully Synchronous Operation for Counting and Programming Internal Carry Look-Ahead Circuitry for Fast Counting Carry Output for n-Bit Cascading Fully Independent Clock Circuit Package Options Include Plastic Small-Outline (D) Packages, Ceramic Chip Carriers (FK), and Standard Plastic (N) and Ceramic (J) 300-mil DIPs
SN54ALS169B, SN54AS169A . . . J PACKAGE SN74ALS169B, SN74AS169A . . . D OR N PACKAGE (TOP VIEW)
U/D CLK A B C D ENP GND
1 2 3 4 5 6 7 8
16 15 14 13 12 11 10 9
VC C RCO QA QB QC QD ENT LOAD
description
These synchronous 4-bit up/down binary presettable counters feature an internal carry look-ahead circuitry for cascading in high-speed counting applications. Synchronous operation is provided by having all flip-flops clocked simultaneously so that the outputs change coincident with each other when so instructed by the count-enable (ENP, ENT) inputs and internal gating. This mode of operation eliminates the output counting spikes normally associated with asynchronous (ripple-clock) counters. A buffered clock (CLK) input triggers the four flip-flops on the rising (positive-going) edge of the clock waveform. These counters are fully programmable; that is, they may be preset to either level. The load-input circuitry allows loading with the carry-enable output of cascaded counters. Because loading is synchronous, setting up a low level at the load (LOAD) input disables the counter and causes the outputs to agree with the data inputs after the next clock pulse.
SN54ALS169B, SN54AS169A . . . FK PACKAGE (TOP VIEW)
A B NC C D
4 5 6 7 8
3 2 1 20 19 18 17 16 15 14 9 10 11 12 13
CLK U/D NC VCC RCO QA QB NC QC QD
NC No internal connection
Copyright © 1994, Texas Instruments Incorporated
The internal carry look-ahead circuitry provides for cascading counters for n-bit synchronous application without additional gating. ENP and ENT inputs and a ripple-carry output (RCO) are instrumental in accomplishing this function. Both ENP and ENT must be low to count. The direction of the count is determined by the level of the up/down (U/D) input. When U/D is high, the counter counts up; when low, it counts down. ENT is fed forward to enable RCO. RCO, thus enabled, produces a low-level pulse while the count is zero (all inputs low) counting down or maximum (15) counting up. This low-level overflow ripple-carry pulse can be used to enable successive cascaded stages. Transitions at ENP or ENT are allowed regardless of the level of the clock input. All inputs are diode clamped to minimize transmission-line effects, thereby simplifying system design. These counters feature a fully independent clock circuit. Changes at control inputs (ENP, ENT, LOAD, or U/D) that modify the operating mode have no effect on the contents of the counter until clocking occurs. The function of the counter (whether enabled, disabled, loading, or counting) is dictated solely by the conditions meeting the stable setup and hold times. The SN54ALS169B and SN54AS169A are characterized for operation over the full military temperature range of 55°C to 125°C. The SN74ALS169B and SN74AS169A are characterized for operation from 0°C to 70°C.
PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters.
POST OFFICE BOX 655303
· DALLAS, TEXAS 75265
ENP GND NC LOAD ENT
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SN54ALS169B, SN54AS169A, SN74ALS169B, SN74AS169A SYNCHRONOUS 4-BIT UP/DOWN BINARY COUNTERS
SDAS125B MARCH 1984 REVISED DECEMBER 1994
logic symbol
9 1 U/D ENT ENP CLK 10 7 2 CTRDIV16 M1 [LOAD] M2 [COUNT] M3 [UP] M4 [DOWN] G5 G6 2,3,5,6+/C7 2,4,5,6 A B C D 3 4 5 6 1, 7D 1 2 4 8 14 13 12 11 QA QB QC QD 3,5CT=15 4,5CT=0 15
LOAD
RCO
This symbol is in accordance with ANSI/IEEE Std 91-1984 and IEC Publication 617-12. Pin numbers shown are for the D, J, and N packages.
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POST OFFICE BOX 655303
· DALLAS, TEXAS 75265
SN54ALS169B, SN54AS169A, SN74ALS169B, SN74AS169A SYNCHRONOUS 4-BIT UP/DOWN BINARY COUNTERS
SDAS125B MARCH 1984 REVISED DECEMBER 1994
logic diagram (positive logic)
LOAD U/D 9 1 15 RCO
ENT ENP
10 7
C1 CLK A 2 3 1D 14 QA
C1 1D B 4 13 QB
C1 1D C 5 12 QC
C1 1D D 6 11 QD
Pin numbers shown are for the D, J, and N packages.
POST OFFICE BOX 655303
· DALLAS, TEXAS 75265
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