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21020285 D User’s Guide
Chapter 4 Command Operation
Page 4 - 14 Some Example Single Commands
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
6. Read the Hardware Status Port at address EE10H. Since the ENT bit of
the Status Port toggles between 0 and 1 with each Single Command
Channel Attention issue, the value returned could be 0202H or 0203H
depending on the previous value. We’ll assume this is the first
command after a reset; the initial value of the ENT bit is 0. The adapter
is ready if the Status Port reads 0202H.
7. To execute the command, write a 0 to the Channel Attention Port.
8. Poll for command completion by reading the Flags Byte of the Status
Block and comparing it to zero. When the value is non-zero, the
command is complete. The value of the Flags byte in the Status Block
will indicate if the command completed with an error. In this example,
the command was successful; a value of 80H is returned as shown
below. A returned value of C0H would indicate an error had occurred.
Figure 15 Single Command Structure in memory