Ciprico Rimfire 3880 User Manual download pdf (Page 32)

21020285 D User’s Guide

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:

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.

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

1 2 ... 27 28 29 30 31 32 33 34 35 36 37 ... 229 230

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Ciprico Rimfire 3880 User Manual Page 32