LayerscapeのトピックRe: ls1046 ddr4 frequency at calibration process

ls1046 ddr4 frequency at calibration process

altu — Thu, 12 Feb 2026 07:38:24 GMT

Good day!

I'm calibrating DDR4 memory on my custom ls1046-based board.

My RCW settings:

SYS_PLL_RAT=6
MEM_PLL_RAT=12
CGA_PLL1_RAT=12
CGA_PLL2_RAT=10

SYSCLK_FREQ=600

DDR_REFCLK_SEL=1
DDR_FDBK_MULT=2

My SYSCLK = 100 Mhz

ddr1.png

I expect to have:

DDR bus clock = 600 Mhz and DDR rate = 1200 MT/s , but I have DDR bus clock = 625 Mhz and DDR rate = 1250 MT/s.

ddr2.png

So the question is - why do we have addtional 25 Mhz / 50 MT/s ?

June_Lu — Fri, 13 Feb 2026 05:27:57 GMT

LS1046A DDR4 Min Freq.(MHz) is 650MHz, as specified in the LS1046A, LS1026A Data Sheet, Table 141. Memory bus clocking specifications

Kindly refer to this requirement in your design.

Thanks

altu — Fri, 13 Feb 2026 07:06:59 GMT

I understand,thank you very much!