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Debugger General Information
3
Device Probe Function
Disk I/O via 162Bug Commands
IOI (Input/Output Inquiry)
3-14
When a disk transfer is requested, the start and size of the transfer is
specified in blocks. The 162Bug translates this into an equivalent sector
specification, which is then passed 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.
A device probe with entry into the device descriptor table is done
whenever a specified device is accessed (i.e., when system calls such as
.DSKRD, .DSKWR, .DSKCFIG, .DSKFMT, and .DSKCTRL, and
debugger commands BH, BO, IOC, IOP, IOT, MAR, and MAW are
used).
The device probe mechanism utilizes the SCSI commands "Inquiry" and
"Mode Sense". If the specified controller is non-SCSI, the probe simply
returns a status of "device present and unknown". The device probe makes
an entry into the device descriptor table with the pertinent data. After an
entry has been made, the next time a probe is done it simply returns with
"device present" status (pointer to the device descriptor).
These following 162Bug commands are provided for disk I/O. Detailed
instructions for their use are found in the Debugging Package for Motorola
68K CISC CPUs User's Manual. When a command is issued to a particular
controller LUN and device LUN, these LUNs are remembered by the
162Bug so that the next disk command defaults to use the same controller
and device.
This command is used to probe the system for all possible CLUN/DLUN
combinations and display inquiry data for devices which support it. The
device descriptor table only has space for 16 device descriptors; with the
IOI command, you can view the table and clear it if necessary.
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