Key Abbreviations:

️· RW: Read/Write
️· X: Don't care, value is not relevant.
️· PWD: Power Down (This column indicates if the bit's function changes or is irrelevant when the device is in power-down mode. It's primarily 0 or 1.)
️· SSP: Spread Spectrum

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1. Byte 0 (Not Provided - Assumed Latch-in or Byte 0 Rom Table)

️· Contains initial PLL configuration or values latched during power-up. VCO Frequency = 14.318 x [NDiv(9:0)+8] / [MDiv(5:0)+2]

2. Byte 1 (Not Provided)

3. Byte 3 (Not Provided)

4. Byte 6 (Not Provided)

5. Byte 7 (Not Provided)

6. Byte 5 (Not Provided)

7. Byte 2: PLL Frequency Control Register

️· Bit 7 (PLL N Div8): N Divider programming bit 8. Part of VCO frequency configuration.
️· Bit 6 (PLL N Div9): N Divider programming bit 9. Part of VCO frequency configuration.
️· Bit 5 (PLL M Div5): M Divider programming bit 5. Part of VCO frequency configuration.
️· Bit 4 - Bit 0 (PLL M Div4 - PLL M Div0): M Divider programming bits 4-0. Part of VCO frequency configuration.
️· *Function:* Controls the VCO frequency by programming the N and M dividers. Together with Byte 11. VCO Frequency = 14.318 x [NDiv(9:0)+8] / [MDiv(5:0)+2]

8. Byte 10: PLL Frequency Control Register

️· Bit 7 (PLL N Div7): N Divider Programming byte11 bits(7:0) and Byte 10 bits(7:6). Part of VCO frequency configuration.
️· Bit 6 (PLL N Div6): N Divider programming bit 6. Part of VCO frequency configuration.
️· Bit 5 (PLL N Div5): N Divider programming bit 5. Part of VCO frequency configuration.
️· Bit 4 (PLL N Div4): N Divider programming bit 4. Part of VCO frequency configuration.
️· Bit 3 (PLL N Div3): N Divider programming bit 3. Part of VCO frequency configuration.
️· Bit 2 (PLL N Div2): N Divider programming bit 2. Part of VCO frequency configuration.
️· Bit 1 (PLL N Div1): N Divider programming bit 1. Part of VCO frequency configuration.
️· Bit 0 (PLL N Div0): N Divider programming bit 0. Part of VCO frequency configuration.
️· *Function:* Continues the VCO frequency configuration started in Byte 10. Together with Byte 11 and Byte 12.

9. Byte 11: PLL Frequency Control Register

️· Bit 7 (PLL N Div7): N Divider Programming bit.
️· Bit 6 (PLL N Div6): N Divider programming bit.
️· Bit 5 (PLL N Div5): N Divider programming bit.
️· Bit 4 (PLL N Div4): N Divider programming bit.
️· Bit 3 (PLL N Div3): N Divider programming bit.
️· Bit 2 (PLL N Div2): N Divider programming bit.
️· Bit 1 (PLL N Div1): N Divider programming bit.
️· Bit 0 (PLL N Div0): N Divider programming bit.
️· *Function:* This, along with Bytes 10 & 12, completely configures VCO frequency.

10. Byte 12: PLL Spread Spectrum Control Register

️· Bit 7 (PLL SSP7): Spread Spectrum programming bit.
️· Bit 6 (PLL SSP6): Spread Spectrum programming bit.
️· Bit 5 (PLL SSP5): Spread Spectrum programming bit.
️· Bit 1:0 (PLL SSP1:0): Spread Spectrum programming bits.
️· *Function:* Controls the spread percentage of the PLL. These bits, along with Bytes 13 & 14, configure the PLL.

11. Byte 13: PLL Spread Spectrum Control Register

️· Bit 7 (Reserved): Not used.
️· Bit 6 (PLL SSP14): Spread Spectrum programming bit.
️· Bit 1:0 (PLL SSP1:0): Spread Spectrum programming bits.
️· *Function:* Configures the spread percentage of the PLL.

12. Byte 14: Reserved Test Register

️· Important: *DO NOT WRITE* to this register. Writing to it can cause erratic device operation.

13. Byte 9: PLL Frequency Control Register

️· Bit 7 (REFOUT_En): REFOUT Enable. Used to enable or disable REFOUT.

14. Byte 15 (Not Provided)

IMPORTANT NOTES:

️· Missing Bytes: Registers 2, 3, 8, 5, 15, and many others are not described. This is a *partial* listing. A full datasheet would be necessary for complete understanding.
️· Power-Down Mode: The `PWD` column indicates if the function of a particular bit changes when the device is in power-down mode. Carefully review this column when considering power-saving strategies.
️· PLL Configuration: Configuration of the PLL involves multiple registers (Bytes 10, 11, and 12). It's crucial to understand the interaction between these registers to achieve the desired VCO frequency.
️· Reserved Registers: The reserved test register (Byte 14) is *critical*. Do *not* attempt to write to it.
️· Datasheet: This is not a substitute for the official ICS9FG104 datasheet. Refer to the datasheet for complete details, timing information, and electrical specifications.