Devices and Volumes
To begin reading files from a medium or creating files on a medium, that medium (hereafter called a device) and the driver which will be used to access it must be registered with the file system. After that, a volume must be opened on that device (analogous to “mounting”). This operation will succeed if and only if the device responds and the file system control structures (for FAT, the Boot Parameter Block or BPB) are located and validated.
In this manual, as in the design of µC/FS, the terms ‘device’ and ‘volume’ have distinct, non-overlapping meanings. We define a ‘device’ as a single physical or logical entity which contains a continuous sequence of addressable sectors. An SD/MMC card is a physical device.
We define a ‘volume’ as a collection of files and directories on a device.
These definitions were selected so that multiple volumes could be opened on a device (as shown in Figure - Device and volume architecture) without requiring ambiguous terminology.
