user manual

Disk I/O Support

B-15

When a disk transfer is requested:

❏ Start and size of the transfer is specified in blocks

❏ 177Bug translates this into an equivalent sector specification

❏ Passes the sector specification on to the controller to initiate

the transfer

If the conversion from blocks to sectors yields a fractional sector

count, an error is returned and no data is transferred.

Device Probe Function

A device probe with entry into the device descriptor table is

performed whenever a specified device is accessed; i.e., when

system calls:

❏ .DSKRD

❏ .DSKWR

❏ .DSKCFIG

❏ .DSKFMT

❏ .DSKCTRL

or debugger commands:

❏ BH

❏ BO

❏ IOC

❏ IOP

❏ IOT

❏ MAR

❏ MAW

are used.