Specifications

©Copyright 2001-2013 SD Group (Panasonic, SanDisk, Toshiba) and SD Card Association
Physical Layer Simplified Specification Version 4.10
21
3.10.4 UHS-II Interface Selection Sequence
UHS-II supported host shall support Legacy SD Bus Interface (I/F) and UHS-II I/F. Removable UHS-II
card slot shall be connected to both I/Fs. Then UHS-II card may be initialized not only in UHS-II mode
but also in SD Bus I/F mode.
Figure 3-19 shows how to select UHS-II mode. After power up, SD bus I/F and UHS-II I/F of UHS-II
card are enabled. UHS-II supported host provides RCLK and STB.L to D0 lane. Host waits D1 lane to
change EIDL to STB.L. If STB.L is detected on D1 lane, host starts UHS-II initialization. If D1 lane is not
changed to STB.L by 200us timeout, host should initialize the card in SD Bus I/F mode. As 200us for
STB.L detection is defined as per card, host needs to determine total timeout value that depends on
UHS-II bus topology of a system.
Figure 3-19 : UHS-II Interface Detection
Figure 3-20 shows abstract of UHS-II Initialization sequence. The first step is PHY initialization. PLL is
activated and synchronized. Before completing PHY Initialization period, SD Bus I/F is disabled. The
second step is Device Initialization. Backend functions of devices are initialized. The third step is
Enumeration. 4-bit unique Device ID is assigned to each device to be able to select one of devices by a
Device ID. The fourth step is Configuration. UHS-II register is set to be able to use UHS-II devices in
optimized bus sequence. The fifth step is SD-TRAN Initialization. UHS-II emulates SD Commands by the
SD-TRAN. SD-TRAN Initialization is equivalent to SD Bus Initialization but host issues SD Commands in
UHS-II packets. UHS-II card accepts most SD commands except some specific commands. Refer to
Section 4.7.5 about the difference of SD command definition in UHS-II. If CMD0 is received, the UHS-II
card re-starts from SD-TRAN initialization.
Figure 3-21 shows SD Bus I/F Initialization sequence for UHS-II Card. UHS-II card shall disable UHS-II
Interface before execution of ACMD41 is completed. If VDD2 is provided during SD Interface initialization
of UHS-II Card, host shall continue to provide VDD2. VDD2 may be off by power cycle with VDD1 before
starting SD Interface initialization. On detecting non UHS-II card, host may turn off VDD2 anytime.
Power Up
Supply VDD1, VDD2
200us Timeout
UHS-II Initialization
Host supplies RCLK and
set STB.L on D0
Host waits D1=STB.L
D1=STB.L
SD I/F Initialization
SD
I/F
UHS-II
I/F
SEL
BE
Card Controller
UHS-II I/F is selected
SD
I/F
UHS-II
I/F
SEL
BE
Card Controller
SD
I/F
UHS-II
I/F
SEL
BE
Card Controller
UHS-II I/F is selected
SD
I/F
UHS-II
I/F
SEL
BE
Card Controller
SD I/F is selected
SD
I/F
UHS-II
I/F
SEL
BE
Card Controller
SD
I/F
UHS-II
I/F
SEL
BE
Card Controller
SD I/F is selected
UHS-II
Card
(Device)
RCLK
V
DD1
V
DD2
D0 = STB.L
D1
UHS-II
Host
EIDL to STB.L
SD
I/F
BE
Card Controller
Legacy SD Card