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| Chapter 4 Command Operation |
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| Some Example Single Commands |
SCSI 6 byte Command Descriptor Block - These six bytes of command information are explained in the SCSI specification.
3.Fill in the Interrupt Word of the Single command Structure. The Interrupt Word is used for the Single Command Interrupt Level.
In this example we'll use an interrupt level of 3, and designate a Status/ ID of 3FH. This means that the adapter will interrupt the Host when the command has completed by driving IRQ3. When requested for its Status/ID during the VME interrupt cycle, the adapter will respond with the value 3FH on lines
In memory, the structure will look like this:
Figure 16 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:
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
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.
5.The example board is jumpered at address EE00H. The three writes to the Address Buffer Port at address EE00H will be as follows:
1.) 843DH
2.) 0008H
3.) 22F4H
21020285 D | User’s Guide |
