Understanding the New UHS-III
In February 2017 the SD Association (SDA) released the SD 6.0
specification, which adds a new level of Ultra High Speed III(UHS-III) bus interface, providing up to 624 megabytes per
second (MB/s) transfer rates.
UHS-III answers the demand for bus speed enhancement for8K videos and 360-degree/3D cameras/drones, and dataintense high-speed wireless communication such as 5G
mobile networks, or IEEE802.11.ax, recorded on higher
capacity SD memory cards. UHS-III includes all UHS-II
functionalities plus 3.12/6.24Gpbs FD modes and Quick
Recovery function. The major modification in UHS-III is theadoption of high-performance PHY. If the host device
implements 6.24Gbps UHS-III PHY, UHS-II devices are
relatively easy to upgrade to UHS-III.

There are four available bitrate segments, called ranges, inUHS-III, as described in Table 1. Range A and B wereintroduced in UHS-II. By 8b/10b coding and half-duplex
mode, setting D0 and D1 lanes to the same direction fordata rate enhancement yields maximum transmission
speeds for Range A and B of 156MB/s and 312MB/s,respectively.
Range C and D are added in UHS-III, achieving thedoubled maximum speeds assured by UHS-III. Maximum
transmission speeds for Range C and D are 312MB/s and624MB/s, respectively, by 8b/10b coding and full-duplex
mode (bus direction switch is not needed). Moreover,“emphasis” technology can be adopted in Range C and D
to improve signal integrity.
Note that a UHS-III memory card must support all ranges
from Range A to Range D.

Key Features of UHS-III
Enhancement of Lane Bitrate
UHS-III interface, which is compatible with UHS-II, consists ofthe following three differential signaling lanes: RCLK, D0 andD1 (see Figure 1). Command, data and other packets orsymbols are transmitted by D0 (basically from host to SDmemory card) and D1 (basically from SD memory card tohost) lanes.

Figure 1: Interface Structure of UHS-III (Full-duplex Mode)

Table 1: Max Bitrate and Transmission Speed for Each Range

Understanding the New UHS-III
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SD memory cards have been progressing in two aspects: greater storage capacity and faster busspeed. Figure 2 shows the progress of SD bus interface throughput. As SDA propels higher storage
capacity and faster bus speed specifications, it enables applications to manage big data with an SD
memory card.

Figure 2: Progress of Bus Interface Throughput

QR Dormant
In UHS-II, once the memory card enters Dormant (power-saving) state, it goes through Wakeup andConfig states to get back to Active state (working). In UHS-III, on the other hand, QR (Quick Recovery)
Dormant function is added to make the transition time from Dormant to Active state shorter. Forexample, the host device can use a UHS-III card in lower power consumption by implementing
efficient power management using QR Dormant if the UHS-III card supports QR Dormant, which canenter deep sleep and return to Active state quickly.

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LLC in the United States, othercountries or both. SD, SDHC,miniSDHC, microSDHC, SDXC
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Figure 3: State Machine for UHS-III

Understanding the New UHS-III
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