Sdio Bus Protocol

Sdio in Host-device mode, all communications are made by host, and device devices can communicate with host as long as the host command is parsed.

Sdio Several wires of the bus:

1. CLK signal: The clock signal of the host to the device.

2. CMD signal: Two-way signal for transmitting commands and reactions.

3. DAT0-DAT3 signal: Four data cable for transmission.

4. VDD signal: power supply signal.

5. VSS1,VSS2: Power ground signal.

In the Sdio bus definition, the DAT1 signal line is multiplexed into a middle wire break. The DAT0 is used to transmit data in the Sdio 1BIT mode, and DAT1 is used as a wire break. DAT0-DAT3 is used to transmit data in the Sdio 4BIT mode, where DAT1 is used as a wire break

The Sdio bus is the host side initiating the request, and then the device side responds to the request. Where the request and the response will be data information.

1. Command: The commands used to start the transfer are sent from the host side to the device side. Where commands are routed through the CMD signal line.

2. Response: The response is the command that the device returns as the host, as a response to a command. is also transmitted through the CMD line.

3. Data: It is transmitted in two directions. Can be set to 1-wire mode or set to 4-wire mode. The data is transmitted through the DAT0-DAT3 signal line.

Sdio each operation is initiated by the host on the cmd line a cmd, for some cmd,device need to return response, some do not need.

For a read command, the host first sends a command to the device, and then the device returns a handshake signal, and when the host receives a handshake signal for the response, it places the data on a 4-bit data line, which is followed by the CRC check code while the data is being transmitted. When the entire read transfer is complete, the host sends a command again notifying the device that the device will return a response.

For a write command, first the host sends a command to the device, and then the device returns a handshake signal, when the host receives a handshake signal from the response, the data is placed on a 4-bit data line, and the data is transferred along with the CRC check code. When the entire write transfer is complete, the host sends a command again notifying the device that the device will return a response.

Sdio card is in the SD memory card interface developed on the basis of the interface, SDIO interface compatible with the previous SD memory card, and can be connected to the Sdio interface device, currently based on the SDIO protocol Spec,sdio interface supports the total class of devices have Bluetooth, network cards, TV cards and so on.

SDIO protocol is an upgrade of the SD Card protocol evolution, many places have retained the SD card read and write protocol, while the SDIO protocol added on the SD card protocol CMD52 and CMD53 commands. Because of this, an important difference between the Sdio and SD card specifications is that the low-speed standard is increased, and the target application of low-speed cards is to support low-speed I/O capabilities with minimal hardware. Low speed cards support applications like modems, barcode scanners, and GPS receivers. High-speed card support network card, TV cards and "combination" card, etc., the combination card refers to the memory +sdio.

Another important difference between the Sdio and the SD card spec is the addition of low-speed standards. The Sdio card requires only SPI and 1-bit SD transfer mode. The target application for low speed cards is to support low-speed I/O capabilities with minimal hardware overhead, and low-speed cards support applications such as modems, bar scanners, and GPS receivers. Full speed and 4BIT operation are mandatory for both the card memory and the SDIO portion of the combo card.

In the SDIO device of the non-combination card, its maximum speed must reach only 25M, and the maximum speed of the card is the same as the highest speed of the SD card, higher than 25M.

Reference from http://blog.csdn.net/luixing67/article/details/5658722

Sdio Bus Protocol