Hi,
I noticed an inconsistency in the LX2160A reference manual regarding the numbering of SerDes 1 lanes.
In section 26.1.4 (SerDes options), SerDes 1 lanes' numbering is reversed when using letters: Lane H = 0 -> Lane A = 7.
In section 26.4.1.19 (SerDes Lane m RX General Control Register 1 (LNARGCR1 - LNHRGCR1)), the text states that the letter numbering is increasing: Lane A = 0 -> Lane H = 7.
I wish to configure register EXT_REC_CLK_SEL in the General Control Register 1, and the address offset for the correct lane depends on this numbering. Can you please confirm which one is correct ?
Best regards.
Hello,
Both sections are correct — they use two different (but consistent) indexing conventions
The apparent contradiction is resolved by understanding that the two sections use different "variables":
Section 26.1.4 — Lane number in the protocol table (H=0 … A=7)
For SerDes 1 specifically, the RM assigns lane numbers from the physical-layer perspective:
| Letter | Lane # (protocol table) |
|---|---|
| H | 0 |
| G | 1 |
| F | 2 |
| E | 3 |
| D | 4 |
| C | 5 |
| B | 6 |
| A | 7 |
This is intentional and correct as documented. NXP TS confirmed this explicitly in a prior case: "SerDes1 has opposite order of lane letters."The same scheme was also confirmed to apply to the LX2160A when a similar question was raised for the LS1046A. The AN13022 application note also uses this same H/0 … A/7 column header.
Section 26.4.1.19 — Register suffix letter as address index (A=0 … H=7)
The offset formula 848h + (a × 100h) uses a as the register-name letter index, where A=0, B=1, … H=7:
| Register name | a (letter index) |
Offset |
|---|---|---|
| LNARGCR1 | 0 | 0x848 |
| LNBRGCR1 | 1 | 0x948 |
| LNERGCR1 | 4 | 0xC48 |
| LNFRGCR1 | 5 | 0xD48 |
| LNHRGCR1 | 7 | 0xF48 |
This is cross-confirmed by AN13022, which lists exactly: "LNmRGCR1 (offsets 0x0848 for lane A, 0x0948 for lane B, 0x0C48 for lane E, 0x0D48 for lane F)"— all consistent with the A=0…H=7 letter-index formula.
How to configure EXT_REC_CLK_SEL for the correct lane
- Identify your lane letter from the SerDes 1 protocol table (section 26.1.4), where the first physical lane is labeled H (lane 0).
- Use the register named after that letter — e.g., for Lane H use
LNHRGCR1, for Lane A useLNARGCR1. - Calculate the address offset using
848h + (letter_index × 100h), where A=0, B=1, …, H=7.
For example, to configure EXT_REC_CLK_SEL on Lane H (the first lane of SerDes 1, lane number 0 in the protocol table):
- Register: LNHRGCR1
- Offset:
848h + 7 × 100h=0xF48
Regards