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User’s Guide 21020285 D
Chapter 4 Command Operation
Some Example Single Commands Page 4 - 13
System Memory address of the Command List structure.
Interrupt = 0300H
Indicates that an Interrupt Level of 3 be used for Command List status.
Command = 01H
This value is the Start Command List command code.
3. Fill in the Interrupt Word of the Single Command structure. This is used
to indicate the Interrupt Level to be used for the Single Command. In
this example we will leave it zero along with the Interrupt Acknowledge
ID. This means the Flags byte of the Status Block will need to be
cleared before issuing the command, and then the Command Complete
(CC) bit polled to determine when this command completes.
In memory, the structure will look like this:
Figure 14 Single Command Structure in memory
4. The next step is to load the Address Buffer Port. This will require three
writes to the port address. Each of the three writes is described next:
Control Field = 84H - For the first write, the Control Field, we’ll select no
byte or word swapping of control structures, but choose to use a 32-bit system
bus.
Address Modifier = 3DH - This is the Address Modifier that the adapter is
to use when reading the Single Command Structure.
Single Command Structure Address = 822F4H - The other two writes
to the port contain the address of the Single Command Structure.