21020285 D User’s Guide
Chapter 4 Command Operation
Page 4 - 12 Some Example Single Commands
Some Example Single Commands
The following examples will help you understand how to use the Single
Command structure. Two examples are given here. The first is an example of
a Board-control command. The second shows you how to issue a Initiator Pass-
through command to the RF3880 adapter.
Example 1:
Start
Command List
Board-control
command
The Start Command List Board-control command sets up a Command List
structure for you to use for subsequent commands. (Basically, the Command
List uses a location in memory as a depot for multiple commands and their
Status Blocks. This feature is discussed in detail later in this chapter.)
This example shows you how to use the Single Command Structure to initiate
the Command List.
1. Select a portion of system memory for the Single Command structure.
You will need 52-bytes of space to hold the Parameter Block, Interrupt
and Reserved fields, and the Status Block that make up a Single
Command structure.
Example Memory Address = 822F4H
2. Fill in the Parameter Block information. (Detailed Parameter Block
information for each Board-control command is given in Chapter 7.)
These are the Parameter Block values for this example:
Command Identifier = 822F4H
Even though the Status Block is part of the Single Command structure and
easily identified it is good to provide a value here in order to be consistent with
Command List structures. The value chosen is the address of the Single
Command structure.
Address Modifier = 3DH
This value indicates that Standard Supervisory Data Access will be used for
Command List data transfers.
ID = FFH
Indicates to the RF3880 adapter that this is a Board- control command.
Command List Memory Address = 99450H
Address
Offset Byte Memory Address
Offset + 0 Offset + 1 Offset + 2 Offset + 3
00H Command Identifier = 000822F4H
04H Reserved Addr Mod = 3DH ID = FFH
08H Command List Memory Address = 00099450H
0CH Reserved Interrupt = 0300H
10H Command = 10H Reserved
14H Reserved
18H Reserved
Table 22: Example Start Command List PB