Ciprico Rimfire 3880 manual Hardware Essentials Channel Attention Port

Chapter 2 Hardware Essentials

Page 2 - 10 Channel Attention Port

Determining a Control Field value - These are the significant points to remember when determining the value you should use for the Control Field:

•The Control Field value is meant to be set once, usually during system initialization. Generally, its value will be set with the first command issued to the board.

•The values you choose for the Control Field will be applied immediately. They will be applicable for the next parameter block read in and all future system memory accesses.

•The Control Field value is never applied to the Address Buffer Port or any of the other hardware ports. Always follow the format given in this section when accessing the hardware ports.

•Attempting to change the Control Field setting after the RF3880 adapter has begun executing a command list will cause unexpected results.

•The default value for the Control Field is zero; the adapter will operate in 16-bit mode and the parameter and status block structures will not be swapped.

Channel Attention Port

Single Command Structure Address Fields

This two-word address is the starting address of the Single Command Structure containing the command to be issued to the board.

The Address Buffer Port is only used when issuing a Single Command to the RF3880 adapter.

The Channel Attention Port is a write-only port. It is used to direct the RF3880 adapter to execute Parameter Block(s) associated with a Command Structure you have already built in system memory. The Channel Attention Port is used for both Single and Command List issue. However, it is written slightly differently in each case (as shown below).

Single Command Channel Attention - To initiate execution of a Single Command you must do the following:

1.Construct a Single Command Structure in system memory.

2.Load the Address Buffer Port with the Control Byte, Address Modifier and the address of the Single Command Structure constructed in Step 1.

3.Write a 0 to the Channel Attention Port, instructing the RF3880 adapter to execute the Parameter Block contained in the Single Command Structure.

Use an offset of 8H from your Base Address when writing to the Channel Attention Port.

21020285 D User’s Guide