DDRPHYC_ACIOCR_ACSR values meaning

[Genadi Zawidowski]

Can anybody say meaning of four values in ACSR field of DDRPHYC_ACIOCR register?

May ill ddr3-equipped board work more stable (i think) if I add no-zero values here...

[PatrickF]

Hi,

it is highly not recommended to change the default/recommended values (I did not have more information on this field).

The only parameters I see which could be tuned to manage signal integrity issues (e.g. on DDR3L board without terminations) is the output impedance (ZPROG[3:0]).

See AN5168.

Regards.

[Genadi Zawidowski]

Yes, my board in 5-th version and now without terminators.

In AN5168 ACSR still hidden. ZPROG related to DQ/DQS lines, in my case I think about address/control lines.

ps: parallelly terminators are can not help me..

[PatrickF]

Hi,

I agree documentation is not clear (even wrong) around this field, we plan to enhance it in next revision.

• ZPROG[3:0] affect output driver impedance. I.e. for DQ/DQS lines (in write direction), as well as AC lines.
• ZPROG[7:4] affect ODT impedance. I.e. for DQ/DQS lines (in read direction).

Btw, you PCB look strange, the AC lines terminations should have been better located at the right of the DDR3L (current should flow from MP15 to DDR3L AC line then to termination resistors.

Regards.