The link above is the correct link. The synthesizers are the same in the Syntor X and Syntor X9000 radios, except for some minor changes in the analog PLL ramp circuit.
Your logic analyzer trace shows two Rx frequencies (S0 is always 1) with the Rx Extender (low band very fancy noise blanker) turned on. Because S0/S1 do not change values, these are only a refresh of the same frequency as last time. S0/S1 are strictly used to control U603 for actual frequency changes, otherwise they stay the same when the frequency does not change. The ADAPT U602 pin 11 signal will tell you when the synthesizer is locked. In the X9k the ADAPT only goes to the squelch hybrid and Q505 to disable the PA deck when the synthesizer is not locked. The X9k U500 processor is not aware of the actual synthesizer unlock/lock state.
Code: Select all
U503 | A3 | A2 | A1 | A0 | D3 | D2 | D1 | D0
U602 | strobe | A2 | A1 | A0 | D3 | D2 | D1 | D0
-------+--------+----+----+----+----+----+----+----
addr 0 | + edge | 0 | 0 | 0 | A3 | A2 | A1 | A0*
addr 1 | + edge | 0 | 0 | 1 | B1 | B0*| A5 | A4
addr 2 | + edge | 0 | 1 | 0 | 0 | 0 | 0 | 0
addr 3 | + edge | 0 | 1 | 1 | B5 | B4 | B3 | B2
addr 4 | + edge | 1 | 0 | 0 | B9 | B8 | B7 | B6
addr 5 | + edge | 1 | 0 | 1 | - | - | - | -
addr 6 | + edge | 1 | 1 | 0 | S1 | S0 | C1 | C0
addr 7 | + edge | 1 | 1 | 1 | V1 | V0 | R1 | R0
R0 = Reference Select - 0 = 6.25 KHz, 1 = 5 KHz
R1 = Reference Select - always 1
S0 = Low Band Width PLL Control, Tx Only - 0 = active
S1 = Frequency Change PLL Control - 0 = frequency change, 1 = no change
C0 = 3/4 Prescaler or Low Band “Rx Extender” On = 0, “Rx Extender” Off = 1
C1 = 3/4 Prescaler or Low Band Always = 1
V0 = VCO Tuning Range Select MSB (not used on 800 MHz radio)
V1 = VCO Tuning Range Select LSB (used on talkaround 800 MHz radio)
Synthesizer 6 bit Word A0, A1, A2, A3, A4, A5
Synthesizer 10 bit Word B0, B1, B2, B3, B4, B5, B6, B7, B8, B9
*A0 and B0 bits are inverted values.
Strobe is a positive edge U602 data input latch control.
S0 controls the U603 PLL RSW (receive) and TSW (transmit) filter selection.
S1 starts the U603 PLL ADAPT and -ADAPT process.
The Low Band Width PLL Control tightens up the PLL accuracy for Tx. Rx is allowed to be a little looser. Presumably for faster synthesizer PLL locks.
Sequence is address 0, 1, 3, 4, 7, 6, 6 (6 is twice to toggle S1/S0 bit values in U602) and finally address 2 (address 2 is the between frequency changes idle state). The two 6s are for the S1/S0 frequency change bit control toggle and are always used even if the frequency is the same as last time and there is no frequency change (S1/S0 do not change values unless the frequency is changed). Each address in the U503 sequence is sent twice by U500 to only toggle the A3 strobe bit (nothing else is changed during a strobe toggle). This strobe toggle enters the U503 output data into the U602 data input. The sequence of strobes are supposed to occur every 20 milliseconds (each individual frequency has multiple strobes and individual frequencies are refreshed every 20 ms, even if the frequency does not change) to keep the 30 millisecond radio Watch Dog Timer from triggering a reset. If you do away with the personality board the Watch Dog Timer goes away.
I measured a positive going Strobe pulse is about 3.24 µs to 3.28 µs wide on about a 10 µs period for each frequency change. This timing might be critical to the U602/U603 PLL lock timing? At least we know this works, any different timing would need testing.
Merry Christmas!