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Debugger General Information
Device Probe Function
A device probe with entry into the device descriptor table is done whenever a
specified device is accessed; i.e., when system calls .DSKRD, .DSKWR,
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.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).
Disk I/O via 166Bug Commands
These following 166Bug 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 166Bug so
that the next disk command defaults to use the same controller and device.
IOI (Input/Output Inquiry)
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.
IOP (Physical I/O to Disk)
IOP allows you to read or write blocks of data, or to format the specified
device in a certain way. IOP creates a command packet from the arguments
you have specified, and then invokes the proper system call function to carry
out the operation.
IOT (I/O Teach)
IOT allows you to change any configurable parameters and attributes of the
device. In addition, it allows you to see the controllers available in the system.
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MVME166 Single Board Computer Installation Guide
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