Make sure that the test computer is in the ready state before you begin your testing. Use of UHS-I requires that the host device command the card to drop from 3. The microSD card has helped propel the smartphone market by giving both manufacturers and consumers greater flexibility and freedom. Provided for compatibility with SD storage-only host controllers. November Learn how and when to remove this template message.

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There are both reversible and irreversible host commands that achieve this. This was superseded by the Speed Class Ratingwhich guarantees a minimum rate at which data can be written to the card.

SD Card I/O Requests (Windows Drivers)

Through issuing various commands, the host device can: The following diagram depicts the SD driver stack that the system creates mivrosoft it enumerates an SD controller and accompanying cards: In other projects Wikimedia Commons. The host device can command the SD card to become read-only to reject subsequent commands to write information to it. Both read and write speeds must exceed the specified value. By the time the version 2.

In applications that require sustained write throughput, such as video recording, the device might not perform satisfactorily if the SD card’s class rating falls below a particular speed. The default computer is the first test computer in the list.

All SD card families initially use a 3. Digital cameras with slow cards may take a noticeable time after taking a photograph before being ready for the next, while the camera writes the first picture. The resulting cards do not digiyal correctly in some host devices. The speed class rating does not totally characterize card performance. This document explains how the operating system supports the card function extensions to SD technology.


Some Windows HLK tests require user intervention. SDIO cards are only fully functional in host devices designed to support their input-output functions typically PDAs like the Palm Treobut occasionally laptops or mobile phones. You must manually configure this computer to have multiple processor groups.

Neither standard formatters nor the SD Association formatter will erase it. By using only commands supported by both standards until determining the type of card inserted, a host device can accommodate both SD and MMC cards.

Choose the type you’d like to provide: You do not need a computer that actually has more than 64 processors to test your device. Indicates that the operation applies to the write-protected property and the state of the WriteProtect switch on the SD card.

A study in found that, in this random-access use, some Class 2 cards achieved a write digihal of 1. Once the host device and the SD card negotiate a bus interface mode, the usage of the numbered pins is the same for all card sizes. The controller can in this way be circumvented.

Secure Digital Host Controller Testing Prerequisites

These limitations may be addressed by evolving memory technologies, with the new SD 7. We’d love to hear your thoughts. SD cards are not the most economical solution in devices zdio need only a small amount of non-volatile memory, such as station presets in small radios. Drivers and devices that do obey a read-only indication may give the user a way to override it.


For tests that do not include a driver to test, such as hard disk drive tests, the Windows HLK scheduler constrains the tests that validate the device’s and driver’s Rebalance, D3 State and Multiple Processor Groups functionality to run on the default test computer.

Speed classes 2, 4, and 6 assert that the card supports the respective number of megabytes per second as a minimum sustained write speed for a card in a fragmented state.


Any secure digital memory card that complies with the requirements of the “Designed for Microsoft Windows” Logo Program for Hardware. November Learn how and when to remove this template message. The card can signal that a response will be delayed, but the host device can abort the dialogue.

Manufacturers may report best-case speeds and may report the card’s fastest read speed, which is typically faster than the write speed. Cards can protect their contents from erasure or modification, prevent access by non-authorized users, and protect copyrighted content using digital rights management.