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===Transfer modes=== {{More citations needed|section|date=September 2023}} Cards may support various combinations of the following bus types and transfer modes. The SPI bus mode and one-bit SD bus mode are mandatory for all SD families, as explained in the next section. 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. * '''SPI bus mode:''' [[Serial Peripheral Interface Bus]] is primarily used by embedded [[microcontroller]]s. This bus type supports only a 3.3-volt interface. This is the only bus type that does not require a host license.{{Citation needed|date=August 2019}} * '''One-bit SD bus mode:''' Separate command and data channels and a proprietary transfer format. * '''Four-bit SD bus mode:''' Uses extra pins plus some reassigned pins. This is the same protocol as the one-bit SD bus mode which uses one command and four data lines for faster data transfer. All SD cards support this mode. UHS-I and UHS-II require this bus type. * '''Two differential lines SD UHS-II mode:''' Uses two [[low-voltage differential signaling]] interfaces to transfer commands and data. UHS-II cards include this interface in addition to the SD bus modes. The physical interface comprises 9 pins, except that the miniSD card adds two unconnected pins in the center and the microSD card omits one of the two V<sub>SS</sub> (Ground) pins.<ref>{{cite web |url=https://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf |title=SD Part 1, Physical Layer Simplified Specification, Version 4.10 |access-date=2014-01-02 |url-status=dead |archive-url=https://web.archive.org/web/20131202232415/https://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf |archive-date=2013-12-02 }}</ref> [[File:MMC-SD-miniSD-microSD-Color-Numbers-Names.gif|thumb|upright|Official pin numbers for each card type (top to bottom): [[MultiMediaCard|MMC]], SD, miniSD, microSD. This shows the evolution from the older MMC, on which SD is based. NOTE: This drawing does not show 8 new UHS-II contacts that were added in spec 4.0.]] {| class="wikitable" style="text-align:center" |+ SPI bus mode |- ! [[MultiMediaCard|MMC]]<br />pin !! SD<br />pin !! miniSD<br />pin !! microSD<br />pin !! Name !! I/O !! Logic !! Description |- | 1 ||1 ||1 ||2 ||nCS ||I ||PP ||style="text-align:left"|SPI Card Select [CS] (Negative logic) |- | 2 ||2 ||2 ||3 ||DI ||I ||PP ||style="text-align:left"|SPI Serial Data In [MOSI] |- | 3 ||3 ||3 ||style="background: gray" | {{sp}} ||VSS ||S ||S ||style="text-align:left"|Ground |- | 4 ||4 ||4 ||4 ||VDD ||S ||S ||style="text-align:left"|Power |- | 5 ||5 ||5 ||5 ||CLK ||I ||PP ||style="text-align:left"|SPI Serial Clock [SCLK] |- | 6 ||6 ||6 ||6 ||VSS ||S ||S ||style="text-align:left"|Ground |- | 7 ||7 ||7 ||7 ||DO ||O ||PP ||style="text-align:left"|SPI Serial Data Out [MISO] |- | style="background: gray" | {{sp}} ||8 ||8 ||8 ||NC<br />nIRQ ||.<br />O ||.<br />OD ||style="text-align:left"|Unused (memory cards)<br />Interrupt (SDIO cards) (negative logic) |- | style="background: gray" | {{sp}} ||9 ||9 ||1 ||NC ||. ||. ||style="text-align:left"|Unused |- | style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||10 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved |- | style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||11 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved |} {| class="wikitable" style="text-align:center" |+ One-bit SD bus mode |- ! [[MultiMediaCard|MMC]]<br />pin !! SD<br />pin !! miniSD<br />pin !! microSD<br />pin !! Name !! I/O !! Logic !! Description |- | 1 ||1 ||1 ||2 ||CD ||I/O ||. ||style="text-align:left"|Card detection (by host) and<br />non-SPI mode detection (by card) |- | 2 ||2 ||2 ||3 ||CMD ||I/O ||PP,<br />OD ||style="text-align:left"|Command,<br />Response |- | 3 ||3 ||3 ||style="background: gray" | {{sp}} ||VSS ||S ||S ||style="text-align:left"|Ground |- | 4 ||4 ||4 ||4 ||VDD ||S ||S ||style="text-align:left"|Power |- | 5 ||5 ||5 ||5 ||CLK ||I ||PP ||style="text-align:left"|Serial clock |- | 6 ||6 ||6 ||6 ||VSS ||S ||S ||style="text-align:left"|Ground |- | 7 ||7 ||7 ||7 ||DAT0 ||I/O ||PP ||style="text-align:left"|SD Serial Data 0 |- | style="background: gray" | {{sp}} ||8 ||8 ||8 ||NC<br />nIRQ ||.<br />O ||.<br />OD ||style="text-align:left"|Unused (memory cards)<br />Interrupt (SDIO cards) (negative Logic) |- | style="background: gray" | {{sp}} ||9 ||9 ||1 ||NC ||. ||. ||style="text-align:left"|Unused |- | style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||10 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved |- | style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||11 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved |} {| class="wikitable" style="text-align:center" |+ Four-bit SD bus mode |- ! [[MultiMediaCard|MMC]]<br />pin !! SD<br />pin !! miniSD<br />pin !! microSD<br />pin !! Name !! I/O !! Logic !! Description |- | . ||1 ||1 ||2 ||DAT3 ||I/O ||PP ||style="text-align:left"|SD Serial Data 3 |- | . ||2 ||2 ||3 ||CMD ||I/O ||PP,<br />OD ||style="text-align:left"|Command,<br />Response |- | . ||3 ||3 ||style="background: gray" | {{sp}} ||VSS ||S ||S ||style="text-align:left"|Ground |- | . ||4 ||4 ||4 ||VDD ||S ||S ||style="text-align:left"|Power |- | . ||5 ||5 ||5 ||CLK ||I ||PP ||style="text-align:left"|Serial clock |- | . ||6 ||6 ||6 ||VSS ||S ||S ||style="text-align:left"|Ground |- | . ||7 ||7 ||7 ||DAT0 ||I/O ||PP ||style="text-align:left"|SD Serial Data 0 |- | style="background: gray" | {{sp}} ||8 ||8 ||8 ||DAT1<br />nIRQ ||I/O<br />O ||PP<br />OD ||style="text-align:left"|SD Serial Data 1 (memory cards)<br />Interrupt Period (SDIO cards share pin via protocol) |- | style="background: gray" | {{sp}} ||9 ||9 ||1 ||DAT2 ||I/O ||PP ||style="text-align:left"|SD Serial Data 2 |- | style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||10 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved |- | style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||11 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved |} Notes: # Direction is relative to card. I = Input, O = Output. # PP = [[Push–pull output|Push-Pull]] logic, OD = [[Open collector|Open-Drain]] logic. # S = [[IC power supply pin|Power Supply]], NC = Not Connected (or [[Pull-up resistor|logical high]]).
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