uMMC Communications Protocol

Communications Protocol

Description

The Protocol for the uMMC employs a simple but robust asynchronous serial control protocol. A command prompt ">" ("greater than" symbol, ASCII 62, HEX 0x3E) indicates that the uMMC is ready to accept a command. A command can be sent, a response will be returned, and the command prompt will be sent again.

Example:

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Command: **`F<>`**

Response: 1>

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If an error occurs while processing a command, an error is returned in the format "Enn". See the table of error codes.

Example:

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Command: **`O 1 R /LOGS/2004/FEBRUARY/FEB30.LOG<>`**

Response: EF2>

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Command Format

C<<sp>>Parameter1<<sp>>Parameter2<<sp>>...<<cr>>

Where:

• C is a single command character.
• <<sp>> is a single space character (ASCII 32, HEX 0x20).
• Parameter1, Parameter2, ... are parameters associated with the command
• <<cr>> is a carriage return character (ASCII 13, HEX 0x0d)

Command Listing Format

C Parameter1 [Parameter2 [Parameter3]]...

• C is the command character. A single character.
• Parameter1 is the first parameter for the command.
• Parameter2 is the second parameter for the command. If it is listed inside of square brackets [ ] then the parameter is optional.

Any parameters listed inside of square brackets [ ] are optional. Most commands that have optional parameters will require the previous parameter to be given.

Command Response Format

In general, responses are of the format:

[[<<sp>>][data]] | [Enn]

Error codes are returned as Enn, where nn is a hexadecimal code indicating the error. See the table of error codes.