HCC4541B

The HCC/HCF4541B Programmable Timer is composed of a 16-stage binary counter, an oscillator controlled by2 external resistorsand a capacitor, an output control logic and an automatic power-on reset circuit. The counter varies on positive-edge clock transation and it can be cleared by the MASTER RESET input. The output from this timer is the Q or Q output from the 8th, 13th, or 16th counter stage. The choice of the stage depends on the time select inputs A or B (see frequency selection table). The output of HCC/HCF4541B is available in one of the twomodes that can be selected via the MODE input, pin 10 (see truth table). The output turns out as a continuous squarewave, with a frequency equal to theoscillator frequency divided by 2^N. When this MODE input is logic " 1 ", when it is a logic " 0 " and after a MASTER
RESET is started, and Q output has been selected, the output goes up to a high state after 2^N-1 counts. It remains in that state till another MASTER RESET pulse is apply or the mode input is a logic " 1 ". The process starts by setting the AUTO RESET input (pin 5) to logic " 0 " and switching power on. If pin 5 is set to logic " 1 ", the AUTO RESET circuit is not enabled and counting cannot start till a positive MASTERRESET pulse is applied, returning to alow level. The AUTO RESET consumes a remarkable amount of power and should not be used if lowpower operation is wanted.

The frequency of the oscillator depends on the RC network. HCC/HCF4541B  can be calculated using the following formula:
f _⁼          1
       2.3 RTC CTC
where f is between 1 kHz and 100 kHz and RS 10 k and 9 2 R_TC