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MC145151P2 Datasheet(PDF) 6 Page - Motorola, Inc |
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MC145151P2 Datasheet(HTML) 6 Page - Motorola, Inc |
6 / 36 page ![]() MC145151–2 through MC145158–2 MOTOROLA 6 12 x 8 ROM REFERENCE DECODER φV MC145152–2 BLOCK DIAGRAM φR 12–BIT ÷ R COUNTER PHASE DETECTOR LOCK DETECT LD fin OSCin OSCout 12 N0 N2 N4 N5 N7 N9 NOTE: N0 – N9, A0 – A5, and RA0 – RA2 have pull–up resistors that are not shown. 10–BIT ÷ N COUNTER CONTROL LOGIC MC 6–BIT ÷ A COUNTER A5 A3 A2 A0 RA2 RA0 RA1 PIN DESCRIPTIONS INPUT PINS fin Frequency Input (Pin 1) Input to the positive edge triggered ÷ N and ÷ A counters. fin is typically derived from a dual–modulus prescaler and is ac coupled into the device. For larger amplitude signals (standard CMOS logic levels) dc coupling may be used. RA0, RA1, RA2 Reference Address Inputs (Pins 4, 5, 6) These three inputs establish a code defining one of eight possible divide values for the total reference divider. The total reference divide values are as follows: Reference Address Code Total Divide Value RA2 RA1 RA0 Divide Value 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 8 64 128 256 512 1024 1160 2048 N0 – N9 N Counter Programming Inputs (Pins 11 – 20) The N inputs provide the data that is preset into the ÷ N counter when it reaches the count of 0. N0 is the least signifi- cant digit and N9 is the most significant. Pull–up resistors en- sure that inputs left open remain at a logic 1 and require only a SPST switch to alter data to the zero state. A0 – A5 A Counter Programming Inputs (Pins 23, 21, 22, 24, 25, 10) The A inputs define the number of clock cycles of fin that require a logic 0 on the MC output (see Dual–Modulus Prescaling section). The A inputs all have internal pull–up resistors that ensure that inputs left open will remain at a logic 1. OSCin, OSCout Reference Oscillator Input/Output (Pins 27, 26) These pins form an on–chip reference oscillator when con- nected to terminals of an external parallel resonant crystal. Frequency setting capacitors of appropriate value must be connected from OSCin to ground and OSCout to ground. OSCin may also serve as the input for an externally–gener- ated reference signal. This signal is typically ac coupled to OSCin, but for larger amplitude signals (standard CMOS logic levels) dc coupling may also be used. In the external reference mode, no connection is required to OSCout. OUTPUT PINS φR, φV Phase Detector B Outputs (Pins 7, 8) These phase detector outputs can be combined externally for a loop–error signal. If the frequency fV is greater than fR or if the phase of fV is leading, then error information is provided by φV pulsing low. φR remains essentially high. If the frequency fV is less than fR or if the phase of fV is lagging, then error information is provided by φR pulsing low. φV remains essentially high. If the frequency of fV = fR and both are in phase, then both φV and φR remain high except for a small minimum time period when both pulse low in phase. MC Dual–Modulus Prescale Control Output (Pin 9) Signal generated by the on–chip control logic circuitry for controlling an external dual–modulus prescaler. The MC level will be low at the beginning of a count cycle and will remain low until the ÷ A counter has counted down from its programmed value. At this time, MC goes high and remains high until the ÷ N counter has counted the rest of the way down from its programmed value (N – A additional counts since both ÷ N and ÷ A are counting down during the first |
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