|00-03||R||Status||Status register, is negativ if an error occured, 0 if idle, 1 if bussy.|
|04-07||RW||Control||Controll register, write to initiate disk operations|
|08-0F||R||Capacity||Total number of sectors of the disk|
|10-17||RW||Sector||sector number of the first sector to be transferred in the next command|
|18-1F||RW||Count||number of disk sectors to be transferred in the next command.|
|20-27||RW||DMA0.address||physical address of first buffer where the next transfer takes place|
|28-2F||RW||DMA0.size||size of first buffer where the next transfer takes place|
|...||RW||DMA1-14||more DMA address and size registers|
|110-117||RW||DMAf.address||physical address of 16th and last buffer where the next transfer takes place|
|118-11F||RW||DMAf.size||size of 16th and last buffer where the next transfer takes place|
The disk simulates a disk controller and the disk proper by using a file of an appropriate size and organization on the host system. The file is read into memory and reread after a RESET or a Power ON. It is considered as a disk immage, that is organizes as a sequence of 512 byte blocks. Disk images can be modified by mounting them as loopback filesystems under Unix with the mount command, or by using the ImDisk Tool under windows.
The disk understands two commands:
The amount of data transferred is specified as an integral number of sectors. The size of a sector size is fixed at 512 bytes. The number of sectors to read or write is given to the controller in the count register. The position of the starting sector on the disk is given to the controller in the sector register. The disk sectors are numbered starting at 0 through (and including) the capacity of the disk minus one. The number of sectors on the disk can be read by software from the capacity register.
The memory buffers from where data is read in a write operation or to where data is written in a read operation is determined by the contents of the 16 DMA register. Each DMA register consists of an address and a size register. It holds the physical address of the buffer and its size. Several buffers can be used in a scatter or gather IO operation. This means that the IO operations view the content of the 16 DMA buffers as one consecutive data area, as if the buffers would have been concatenated. For example a write operation with gather its data first from buffer number one then from buffer number two, and so forth until the number of sectors requested are written or the buffers are all written. A read operation will scatter the sectors read from disk by filling the first buffer and then the second, until all disk sectors are written to memory or the bufferes are all filled.
The 3 low order bits of the control register are used to control the disk. These bits are from low order to high order:
The status register is read only. Only two bit are significant, the first and the last.
Tesing the status register, there are three typical values: negative means error, 1 meand bussy, 0 means idle.
|host||localhost||the host where the bus is located|
|port||9002||the port where the bus is located|
|address||default||address where the resource is located|
|interrupt||not set||interrupt sent when character is ready|
|file||not set||Name of the file containing the disk image|
|x||0||the x position of the window|
|y||0||the y position of the window|
|minimized||false||start with a minimized window|
|debug||false||to generate debug output|
|debugmask||0xFFF0||set mask to hide debug output|
|verbose||false||make debugging verbose, sets debug mask to zero|
|define||not set||to define a name for conditionals|
|config||not set||filename for a configuration file|
|help||false||to print information|
These can be set in default.vmb