User Manual

SECTION 3
3-1
Part No. 001-3422-003
PROGRAMMING
3.1 INTRODUCTION
The DL-3422 information in Section 3.2 describes synthesizer programming protocol. This information can
be used as a basis for designing the synthesizer programming hardware and software.
The DL-3422 VHF Transceiver uses a high performance Fractional-N Synthesizer and Voltage Controlled
Oscillator (VCO). The Fractional-N Synthesizer offers high frequency resolution, fast lock times, and improved
noise performance over conventional synthesis techniques. With conventional synthesizers, the phase detector
comparison frequency must be equal to the channel spacing because the main divider can only change in integer
steps. The channel spacing (resolution) of a Fractional-N synthesizer is a fraction of the comparison frequency.
With the Fractional-N synthesizer, the comparison frequency is increased to 5 or 8 times the channel step
frequency. The total loop division is reduced with a higher comparison frequency which improves phase noise.
Lock times are improved because the loop bandwidth can be wider.
3.2 DL-3422 SYNTHESIZER DATA PROTOCOL
3.2.1 INTRODUCTION
Programming the SA-7025 synthesizer IC (U811) is accomplished via the 3-line bus; DATA, CLOCK, and
STROBE. Four 24 bit words (D, B, C, and A0) are required to load the synthesizer. The D, C, and B words
contain four address bits each; the A0 word has a 1 bit address. Synthesizer frequency acquisition is initiated
when the A0 word is loaded. We recommend using modulus 3 and sending the D, B, C, and A0 words for each
synthesizer load (LONG load). When the STROBE = low, the clock driver is enabled and the DATA is clocked
into the shift registers on the positive edges of the CLOCK. When STROBE = high, the clock is disabled and the
data in the shift registers remain stable. The DATA is latched into different working (or temporary) registers
depending on the address bit(s). In order to fully program the synthesizer, all four words must be sent with the
A0 word sent last. Refer to Table 3-1 and Figure 3-3 for data format information.
3.2.2 PROGRAMMING SYNTHESIZER PARAMETERS
The DL-3422- RF Board is available in three frequency ranges, 132-150 MHz (Band 4), 150-174 MHz
(Band 5), and 150-174 MHz (Band 6). Band 6 was designed to be compatible with the FCC’s refarmed VHF
band plan therefore, 2.5 kHz channel resolution is used. The Band 4 and 5 versions can be programmed for 5,
6.25, and 7.5 kHz steps depending on user requirements.