Personal Computer User Manual

Disk I/O Support
MVME197LEIG/D1 3-11
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made, the next time a probe is done it simply returns with “device present”
status (pointer to the device descriptor).
Disk I/O via 197Bug Commands
These following 197Bug commands are provided for disk I/O. Detailed
instructions for their use are found in the MVME197BUG 197Bug Debugging
Package User’s Manual. When a command is issued to a particular controller
LUN and device LUN, these LUNs are remembered by 197Bug so that the next
disk command defaults to use the same controller and device.
IOI (Input/Output Inquiry)
IOI allows the user 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, the user can view the table and clear it if necessary.
IOP (Physical Input/Output to Disk)
IOP allows the user 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
specified by the user, and then invokes the proper system call function to carry
out the operation.
IOT (Input/Output Teach)
IOT allows the user to change any configurable parameters and attributes of
the device. In addition, it allows the user to see the controllers available in the
system.
IOC (Input/Output Control)
IOC allows the user to send command packets as defined by the particular
controller directly. IOC can also be used to look at the resultant device packet
after using the IOP command.
BO (Bootstrap Operating System)
BO reads an operating system or control program from the specified device
into memory, and then transfers control to it.
BH (Bootstrap and Halt)
BH reads an operating system or control program from a specified device into
memory, and then returns control to 197Bug. It is used as a debugging tool.