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LMK04808: What does the reserved bit in R31 mean?

Part Number: LMK04808

Hi team,

What does the reserved bit in R31 mean?

The issue is PLL1 loses lock. We did 2 tests.

1. compare all the register readback, only R31 is different. please check the results below:

R0:0x140300
R1:0x140181
R2:0x140182
R3:0x140303
R4:0x140304
R5:0x140185
R6:0x11110006
R7:0x11110007
R8:0x11110008
R9:0x55555549
R10:0x1002410a
R11:0x40c300b
R12: 0xb0c01ac
R13: 0x1301866d
R14:0x100000e
R15:0x8010800f
R16:0x1550410
R24:0x883000d8
R25:0x1080019
R26:0x8fa0401a
R27:0x1c00201b
R28:0x10021c
R29:0x61d
R30:0x200061e
R31:0x9900103f //bad chip
R31:0xf900103f //good chip

2. ref clk is send to clockin0 in system, we connect a copy of ref clk to clockin1 and the chip is recover. All the regiter read back value is the same as good chip.

B&R
Lijia