Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 4/01/2024
Public

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5.4.6.4. Clocks

The following table describes the input clocks used by the SD/eMMC host controller and combo PHY when used in the SD/eMMC mode.

Table 219.  SD/eMMC Host Controller Clock Inputs
Clock Description
s_pclk This clock input is supplied from the APB clock.
clk This clock input is supplied from the AXI interface clock.
sdphy_reg_pclk Clock utilized by the APB interface that connects the host controller APB requester and combo PHY APB completer.
sdmclk This is the SD functional clock. It supplies the card interface unit/logic in the SD and eMMC mode.

All the above clocks are sourced from the l4_mp_clk coming from the clock manager. The allowed l4_mp_clk clock frequency range is 50..200 MHz. You can gate all the clocks to the SD/eMMC host controller through the clock manager by using the perpllgrp.en.sdmmcclken register bitfield.

The following figure shows more details about the clocking of the SD/eMMC host controller and combo PHY.

Figure 144. SD/eMMC Clocking

The dfi_ctrl_sel[0] signal coming from system manager selects between enabling NAND and SD/eMMC as they are mutually exclusive and they share the same combo PHY. When SD/eMMC is enabled, the SD/eMMMC sdmclk clock and combo PHY clk_phy, and clk_ctrl clocks all have the same value. The l4_mp_clk is typically 200 MHz, and with the available 1/2/4 divider, so this clock can have the 200/100/50 MHz value. The SD card clock is obtained by dividing this clock by either 1 or a multiple of 2. Typical values for the clock are shown in the table below.

Table 220.  Typical SD/eMMC Controller Clock Frequencies
Device Type Transfer Mode Transfer Speed Controller Frequency
SD SDR12 12.5 MB/s 50 MHz 23
SDR25 25 MB/s 50 MHz
SDR50 50 MB/s 100 MHz
SDR104 100 MB/s 24 200MHz
DDR50 50 MB/s 50 MHz
eMMC Legacy 25 MB/s 50 MHz23
High-speed SDR 50 MB/s 50 MHz
High-speed DDR 100 MB/s 100 MHz
HS200 (SDR) 200 MB/s 200 MHz
HS400 (DDR) 400 MB/s 200 MHz

More information:

  • Refer to Clock Manager chapter for more information about clocking.
  • Refer to Combo DLL PHY chapter for more details about the Combo PHY operation.
23 The clock to the SD card is the controller clock divided by 2 in these cases, and by 1 in all other cases.
24 To obtain the 104 MB/s, a controller clock of 208 MHz is needed. With a maximum clock of 200 MHz, only 100 MB/s can be obtained.