Interphase Tech 4221 Field Offset, Contiguous Data Allocation

Chapter 3 - MACSI Host Interface

Field Offset

The value in the far left column specifies the field offset. This value measures increments of 16 bits from the beginning of the record, and may be thought of as the displacement to be added to a pointer to short integer data type required to differentiate the particular field.

Onboard Command Queue Entry

Offst	15	14	13	12	11	10	9		8	7	6	5	4	3	2	1	0
0x00						Queue Entry Control Register
0x01								Reserved

This construct is indicated by the term Offst appearing in the table heading, and is used for objects that may appear in different locations, either in host system memory or the Short I/O space.

Contiguous Data Allocation

Finally, contiguous allocated space may be specified with a starting address and an ending address, as follows:

Command Response Block

Addr	15	14	13	12	11	10	9		8	7	6	5	4	3	2	1	0
0x73A								Reserved
to								(8 Bytes)
0x73E

For addresses, the final number will always represent the last byte address of the allocated space. For offsets, it represents the final offset location, as follows:

Initialize Controller

Offst	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0x07					Controller Initialization Block Offset
0x08							Reserved
to							(20 Bytes)
0x11

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