The MC1451591 has a programmable 14bit reference counter, as well as fully programmable dividebyN/dividebyA counters. The counters are programmed serially through a common data input and latched into the appropriate counter latch, according to the last data bit (control bit) entered. When combined with a loop filter and VCO, this device can provide all the remaining functions for a PLL frequency synthesizer operating up to the device's frequency limit. For higher VCO frequency operations, a down mixer or a dualmodulus prescaler can be used between the VCO and the PLL.