Difference between revisions of "83Plus:Software:usb8x/Asm Interface/MSD"

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== Entry Points ==
 
== Entry Points ==
  
If all three of the initializing U_CALLs succeed, the following entry points can then be called.
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If all three of the initializing U_CALLs succeed, the other following entry points can then be called.
  
 
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Revision as of 02:23, 17 August 2006

The mass storage driver works through a series of U_CALL entry points, much like the HID driver.

It requires two RAM buffers, one for internal use and one for a sector buffer. File handles used for opened files (explained later) also require around 27 bytes. The size of all three of these buffers can be obtained through the MSDVersion U_CALL. The size of the internal buffer is typically 254 bytes and the sector buffer is 512 bytes.

The entry point which requires these buffers is the MSD_Initialize U_CALL. Its memory can be dynamically allocated to appBackUpScreen (taking up practically all of it) with the code below:

U_CALL MSDVersion
ld de,appBackUpScreen
push de
add hl,de
ex de,hl
pop hl
U_CALL MSD_Initialize

For file system operations, you will then make calls to UFI_Initialize and FAT_Initialize. All entry points will return with the carry flag set if there are problems, with more detailed information in offErrorCode.

No knowledge of the intimate details of FAT16 are required. However, the "starting cluster" of a directory is used in several routines. This is a 16-bit number uniquely indentifying a directory. It is beneficial to use this number rather than an extremely long ASCIIZ directory path which wastes memory. It is easily obtained with FAT_getStartingCluster by passing an ASCIIZ directory path to it.

Entry Points

If all three of the initializing U_CALLs succeed, the other following entry points can then be called.

MSDVersion Gets mass storage driver version and memory requirements
MSD_Initialize Initializes mass storage driver
UFI_Initialize Initializes connected mass storage device for sector read/write operations
UFI_Read Reads sector at (MSDLBA) address into sector buffer
UFI_Write Writes memory in sector buffer to (MSDLBA) address
FAT_Initialize Initializes connected mass storage device for FAT16 file system operations
DOS_openFile Opens a file and populates file handle with important information
DOS_fileSeek Sets seek pointer for file handle to specified offset
DOS_fileRead Read bytes from a file
DOS_fileWrite Write bytes to a file and grow if necessary
DOS_createFile Create new file in specified directory with size 0
DOS_createDirectory Create new subdirectory in specified directory
DOS_renameFileEntry Rename specified file or folder
DOS_deleteFileEntry Delete file or folder (including contents)
DOS_countFilesInDir Get number of files/folders in specified directory
DOS_getNextFile Get first/next file in specified directory
DOS_getFileSize Get size of file
DOS_getDirEntry Get directory entry for specified file/folder
FAT_nameConvertTo11 Convert name to 11-character format (ex. "README TXT")
FAT_nameConvertFrom11 Convert name to ASCIIZ format (ex. "readme.txt")
FAT_lookupPath Find whether specified file/directory exists
FAT_findFileInCluster Get directory entry for a file in specified folder
FAT_getStartingCluster Get starting cluster of specified directory
MSD_ImportVariable Imports 8x* file in specified directory as calculator variable in RAM/Flash
MSD_ExportVariable Exports calculator variable in RAM/Flash as 8x* file in specified directory