Circuit knowledge

The generator described is a good value·for money alternative to the commercially available types; it uses  only one CMOS-IC 4060 and provides up to seven different baud rates. Lets learn more regarding the pin out configuration of the IC 4060.

Each serial data interface requires a baud rate generator: terminal, printer tape interface. . . lt is often not possible to use the same generator for input and output, so it would be useful to add one to, for instance, the UART in the computer or the UART in the terminal. To keep the ,costs of such an addition down, we have developed a generator which uses just one IC, two resistors, one preset potentiometer and a capacitor. The CMOS 4060 is a 14-stage binary counter with an internal oscillator which only requires the frequency determining RC components. As the reset is connected to earth, the counter begins to count upwards when the supply is switched on. A clock frequency then becomes available at the outputs: the higher the number of the output, the lower the frequency available at it.

 In the circuit shown the frequencies avail- able at the various outputs are: O4 = 9600 baud 08 = 600 baud 05 = 4800 baud O9 = 300 baud O6 = 2400 baud Q10 = 150 baud Q7 = 1200 baud If the outputs are wired as shown in the circuit diagram, the required baud rate can then be selected by means of a wire link. _ The oscillator frequency can be set precisely with P1, and measured either at pin 9 of the 4060 or at one of the outputs O4 . . . Q10. With the values shown, the frequency at pin 9 should be 38.4 kl-lz; at the outputs O4. . .010 the relevant baud rate. lt is often required that the clock frequency is 16 times the baud rate (for instance, with asynchronous ~ operation of the 6850, 8251, 280- SIO. . .). ln that case, C1 must be replaced by a 27 nF capacitor and the oscillator frequency must be set to 614.4 kHz.