Ciprico Rimfire 3880 Hardware Essentials Address Buffer Port, Address Buffer Port Writes

Chapter 2 Hardware Essentials

Page 2 - 8 Address Buffer Port

Address Buffer Port

The Address Buffer Port is a write-only port. It is used when you wish to execute a command using a Single Command Structure (SCS). It is loaded with: the starting system address of the structure; an

address modifier value to be used when reading the Parameter Block contained in the structure; and a byte of control information through which you may instruct the RF3880 adapter about subsequent operation.

The Address Buffer Port register is three words deep and 16 bits wide. To pass all three words requires three writes to the port:

•The first write must contain the Control byte and Address Modifier.

•The second write contains the Most Significant Word (MSW) of the Single Command Structure address in system memory.

•The last write contains the Least Significant Word (LSW) of the Single Command Structure address.

The order of these writes is illustrated in the following figure:

Bits	15		8	7		0
1st Write		Control			AM Bits for SCS
2nd Write		Single Command Structure Address: MSW
3rd Write		Single Command Structure Address: LSW

Table 6: Address Buffer Port Writes

A description of each of the fields of the Address Buffer Port follows.

Address Modifier Field

The Address Modifier (AM) Field of the Address Buffer Port is used to specify the Address Modifier value that the RF3880 adapter should use when reading the first Parameter Block.

21020285 D User’s Guide