topic Re: i.MX6D Precharge Timer PRCT in i.MX Processors

i.MX6D Precharge Timer PRCT

sugiyamatoshihi — Fri, 22 Sep 2017 02:55:09 GMT

Hi,

I'd like to know how to chose the value of PRCT (Precharge Timner) in MMDCx_MDPDC?

Default is disabled, but what will change when this value chose other than default value.

Best Regards,

Sugiyama

Re: i.MX6D Precharge Timer PRCT

Yuri — Fri, 22 Sep 2017 07:52:22 GMT

Hello,

"Auto precharge is a feature that performs the same individual bank PRECHARGE function [...]

without requiring an explicit command". You look at auto precharge feature explanation on Micron Web.

Micron Technology, Inc. - 512Mb: x16, x32 Mobile LPDDR SDRAM (Recommended for new designs)

In i.MX6 MMDC by default this feature is disabled. This allows to access previous active page, defined

by DRAM row number, without additional clocks for new page activation. So, setting non-default PRCT

may sometimes cause some performance penalty. But if new memory access is performed for other

DRAM page, one can get additional clocks for previous page precharging.

Have a great day,
Yuri

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Re: i.MX6D Precharge Timer PRCT

sugiyamatoshihi — Mon, 25 Sep 2017 07:49:05 GMT

Hi, Yuri,

Thank you for the answer. I read Micron Web.

I'd like to confirm.

I think when PRCT=00 means disable automatic Pre-charge, it use tRP in MMDCx_MDCFG1.

Then PRCT (!=00) is used as Precharge command period at Automatic Precharge instead of tRP.

Does it means PRCT should be set the same delay value of tRP(value depend on memory) for Automatic Precharge?

Best Regards,

Sugiyama

Re: i.MX6D Precharge Timer PRCT

Yuri — Mon, 25 Sep 2017 09:47:35 GMT

Hello,

the PRCT parameter just defines the period from last activity to precharge command.

(Assuming the data in current active row are not "interesting" more for fast access.)

tRP - Row Precharge Time:
tRP is the number of clock cycles taken between the issuing of the precharge command and

the active command. In this time the sense amps charge and the bank is activated.

tRAS, tRCD, tRP, tRC ? | TechPowerUp

So, PRCT and tRP are different parameters.

Regards,

Yuri.

Re: i.MX6D Precharge Timer PRCT

sugiyamatoshihi — Mon, 25 Sep 2017 10:08:04 GMT

Hi, Yuri,

Thanks.

If Auto Precharge PRTC use, what DDR parameter should refer to?

Best Regards,

Sugiyama

Re: i.MX6D Precharge Timer PRCT

Yuri — Tue, 26 Sep 2017 05:22:47 GMT

Hello,

I would say, the PRCT is application depended parameter, but - not DDR related.

Regards,

Yuri.

Re: i.MX6D Precharge Timer PRCT

sugiyamatoshihi — Tue, 26 Sep 2017 08:28:23 GMT

Hi, Yuri,

I' sorry I missed spell. It is PRCT.

I confused its value is depend on application because that is described below. I thought it related DDR parameter.

Automatic precharge of all DDR banks to a specific chip select. Can be activated by
configuring ESDPDC fields: PRCT_0 and PRCT_1. Each field determines a value
loaded to a different chip select.

However, according to your comment, does PRCT define how many idle cycle of DDR count before issue DDR Precharge command at the power down sequence?

Best Regards,

Sugiyama

Re: i.MX6D Precharge Timer PRCT

Yuri — Wed, 27 Sep 2017 09:10:18 GMT

Hello,

Automatic precharge of all DDR banks may be used for power saving, assuming

active page consume more power.

Regards,

Yuri.

Re: i.MX6D Precharge Timer PRCT

sugiyamatoshihi — Mon, 02 Oct 2017 01:57:19 GMT

Hi, Yuri,

Thanks.

I understood PRCT is for system power saving mode not DDR timing.

Best Regards,

Sugiyama