Rwabs() is the function used to read (resp. write) sectors from (resp. to) a block device to (resp. from) memory.

4 (0x04)

All TOS versions.

mode is a bitmask of operation to perform:

Name	Value	Bit number in mode	Bit=0	Bit=1
RW_READ	0	0	Read operation	-
RW_WRITE	1	0	-	Write operation
RW_NOMEDIACH	2	1	Operation can update media change status	Operation does not update media change status
RW_NORETRIES	4	2	Operation is retried on error condition	Operation is not retried on error condition
RW_NOTRANSLATE	8	3	Operation is in logical mode	Operation is in physical mode

buf is a pointer to a block of memory large enough to contain the amount of bytes that will be read or written by the operation. Its size must be count * logical sector size in logical mode, or count * 512 in physical mode.

count is the number of sectors that will be transferred during operation. Note: it is a WORD value, thus limited to 32767 sectors per operation.

recno is the number of the first sector to transfer. Note: it is a WORD value, thus you can only specify a start sector up to 32767. If your hard disk driver (above AHDI 3.0) supports it, you can use lrecno parameter to pass a LONG value, thus allowing access to many more sectors, in this case, set recno to -1.

dev is the device number on which to perform operation. In logical mode, it is associated to drive letters: 0 for device 'A:', 1 for 'B:', and so on. In physical mode, device number is as follows:

Device number	Devices
0 - 1	Floppy devices 0 - 1
2 - 9	ACSI devices 0 - 7
10 - 17	SCSI devices 0 - 7
18 - 19	IDE devices 0 - 1

lrecno is the number of the first sector to transfer.

	move.l	#lrecno,-(sp)
	move.w	#dev,-(sp)
	move.w	#recno,-(sp)
	move.w	#count,-(sp)
	pea	buf
	move.w	#mode,-(sp)
	move.w	#4,-(sp)
	trap	#13
	lea	18(sp),sp

Rwabs() returns E_OK (0) if no error occured, or a negative BIOS error code.

Getbpb(), XHReadWrite()