Agilex™ 7 Hard Processor System Technical Reference Manual

ID 683567
Date 8/13/2024
Public
Document Table of Contents

13.5. Preserving SDRAM Contents

Note: The SDRAM preservation feature is available for Agilex™ 7 M-Series during HPS Cold, Watchdog, and Warm resets. This feature is not available for the Agilex™ 7 F-Series and Agilex™ 7 I-Series during HPS Cold reset nor Watchdog timeout configured for HPS Cold Reset.

To preserve SDRAM contents, you must enable the External Memory Interface (EMIF) fence and drain functionality using the Reset_Mgr.hdsken.mpfe_hmca_drainen register bit.

If EMIF fence and drain functionality is enabled, the Reset Manager hardware issues a fence and drain request to the MultiPort Front End (MPFE) by asserting the f2sdram_fence_and_drain_req signal. The MPFE then stops accepting new read or write requests. The MPFE keeps track of how many transactions there are in flight at any time, so once it has seen the fence and drain request and all the outstanding transactions are completed, the MPFE issues an acknowledge to the Reset Manager by asserting the f2sdram_fence_and_drain_ack signal to indicate that it is safe to actually perform the reset of the MPFE. This action does not reset the HMC that is controlling the SDRAM, and thus SDRAM contents are preserved. If the Reset Manager does not receive an acknowledgement within a specified period (value set in Reset_Mgr.hdsktimeout register which defaults to 10,240 l4_sys_free_clk cycles), then it resets the MPFE regardless.

If EMIF fence and drain functionality is not enabled, then the Hard Memory Controller (HMC) resets to clear any outstanding transactions. In this case, SDRAM contents should be assumed to be lost.

Table 107.  Preserving SDRAM contents for Agilex™ 7 F/I-Series
Agilex™ 7 F/I-series
EVENT EVENT trigger Pre-EVENT trigger setup Post-EVENT trigger execution SDRAM preserved?
HPS Warm Reset
  • SW/Mailbox
  • Reset_Mgr.mpul2flushtimeout
  • Reset_Mgr.hdsktimeout
  • Reset_Mgr.hdsken.l2flushen
  • Reset_Mgr.hdsken.mpfe_hmca_drainen
  • L2 cache flush is performed.
  • Fence & Drain is performed.
  • HPS Warm Reset is performed, and HMC is not reset.
Yes
  • Watchdog
  • L2 cache flush is not performed.
  • Fence & Drain is performed.
  • HPS Warm Reset is performed, and HMC is not reset.
Yes
HPS Cold Reset
  • SW/Mailbox

  • HPS_COLD_nRESET pin
  • Watchdog
  • L2 cache flush is not performed.
  • Fence & Drain is performed.
  • HPS Cold Reset is performed, and HMC is reset.
No
Table 108.  Preserving SDRAM contents for Agilex™ 7 M-Series
Agilex™ 7 M-Series
EVENT EVENT trigger Pre-EVENT trigger setup Post-EVENT trigger execution SDRAM preserved?
HPS Warm Reset
  • SW/Mailbox
  • Reset_Mgr.mpul2flushtimeout
  • Reset_Mgr.hdsktimeout
  • Reset_Mgr.hdsken.l2flushen
  • Reset_Mgr.hdsken.mpfe_hmca_drainen
  • L2 cache flush is performed.
  • Fence & Drain is performed.
  • HPS Warm Reset is performed, and HMC is not reset.
Yes
  • Watchdog
  • L2 cache flush is not performed.
  • Fence & Drain is performed.
  • HPS Warm Reset is performed, and HMC is not reset.
HPS Cold Reset
  • SW/Mailbox
  • HPS_COLD_nRESET pin
  • Watchdog
  • L2 cache flush is not performed.
  • Fence & Drain is performed.
  • HPS Cold Reset is performed, and HMC is not reset.