UHS-III Interface Sets 624 MB/sec SD Card Transfer Rate Standard

The SD Card association (SDA) has released the SD 6.0 specification which adds a new level of UHS-III bus interface, providing up to 624 MB/sec transfer rates. This update to the Ultra High Speed standard directly answers the demand for 8K, 360-degree and 5G IEEE802.11ax mobile network support. The upgrade is fully backwards compatible and includes all the functionalities of the UHS-II standard with the addition of 3.12/6.24 Gpbs FD modes and Quick Recovery function.

There are four available bitrate segments in UHS-III, the first two Range A and B were introduced with UHS-II, having an RCLK frequency of 26-52MHz. By 8b/10b coding and half-duplex mode, setting D0 and D1 lanes to the same direction for data rate enhancement yields maximum transmission speeds for Range A and B of 156MB/s and 312MB/s, respectively. The two other Range C and D added in UHS-III has an RCLK frequency of 48-52MHz and by 8b/10b coding and full-duplex mode (bus direction switch is not needed), it can reach transmission rates of 312MB/s and 624MB/s, respectively. A UHS-III card must support all ranges from A through D. SD memory cards have been progressing in two aspects: greater storage capacity and faster bus speed. As SDA propels higher storage capacity and faster bus speed specifications, it enables applications to manage big data with an SD memory card.

The UHS-III standard’s quick recovery function is designed so it can enter active state much quicker. In UHS-II, before the SD card can enter the dormant power saving state, it has to go through Wake-up and Config states first in order to get back to a working Active state. In UHS-III, the SD card can use a Quick Recovery Dormant (QR dormant) function to shorten the time it needs to reach Active state.