CD74HC4059

The 'HC4059 are high-speed silicon-gate devices that are pin-compatible with the CD4059A devices of the CD4000B series. These devices are divide-by-N down-counters that can be programmed to divide an input frequency by any number "N" from 3 to 15,999. The output signal is a pulse one clock cycle wide occurring at a rate equal to the input frequency divide by N. The down-counter is preset by means of 16 jam inputs.

The three Mode-Select Inputs Ka, Kb and Kc determine the modulus ("divide-by" number) of the first and last counting sections in accordance with the truth table. Every time the first(fastest) counting section goes through one cycle, it reduces by 1 the number that has been preset (jammed) into the three decades of the intermediate counting section an the last counting section, which consists of flip-flops that are not needed for opening the first counting section. For example, in the ÷2 mode, only one flip-flop is needed in the first counting section. Therefore the last counting section has three flip-flops that can be preset to a maximum count of seven with a place value of thousands. If ÷10 is desired for the first section, K_a is set "high", K_b "high" and K_c "low". Jam inputs J1, J2, J3, and J4 are used to preset the first counting section and there is no last counting section. The intermediate counting section consists of three cascaded BCD decade (÷10) counters presettable by means of Jam Inputs J5 through J16.

The Mode-Select Inputs permit frequency-synthesizer channel separations of 10, 12.5, 20, 25 or 50 parts. These inputs set the maximum value of N at 9999 (when the first counting section divides by 5 or 10) or 15,999 (when the first counting section divides by 8, 4, or 2).

The three decades of the intermediate counter can be preset to a binary 15 instead of a binary 9, while their place values are still 1, 10, and 100, multiplied by the number of the ÷N mode. For example, in the ÷8 mode, the number from which counting down begins can be preset to:
       3rd Decade                         1500
       2nd Decade                          150
       1st Decade                             15
       Last Counting Section        1000
The total of these numbers (2665) times 8 equals 12,320.The first counting section can be preset to 7. Therefore,21,327 is the maximum possible count in the ÷8 mode.

The highest count of the various modes is shown in the Extended Counter Range column. Control inputs K_b and K_c can be used to initiate and lock the counter in the "master preset" state. In this condition the flip-flops in the counter are preset in accordance with the jam inputs and the counter remains in that state as long as K_b and K_c both remain low. The counter begins to count down from the preset state when a counting mode other than the master preset mode is selected.