User`s manual

SBCSCSI/D1B-1

SIOP FIRMWARE

STRUCTURES

Introduction

This appendix lists all of the structures which are external to or defined by the

SIOP Firmware and which must be provided by the code using the services of

the Firmware.

siop_struc (Command Structure)

The command structure contains all the information necessary to manage a

single call to the SIOP Firmware. This structure is initialized by the user and

allocated to the Firmware when the user makes a command call to the

Firmware. This structure consists of control information, command

information, and various pointers. Each field is defined for the command

mode in which it is used. The INTATR bit, the TARGET bit, and the CONFIG

bit in the Command Control field are mutually exclusive. The Firmware can

operate in only one mode per command. If more than one of these bits are set

in a single command structure then the results are unpredictable. Once this

structure is allocated to the Firmware the user cannot modify any field within

it until the structure is released at status time. The command structure must

be aligned on a four-byte boundary (longword for the CISC MVME162

/166/167; word for the RISC MVME187/197).

Cache coherency for the command structure is the responsibility of the user.

Generally, on all supported SBCs except the MVME187, the proper snoop

mode setting (refer to Table B-5) handles the cache coherency. On the

MVME187, it is suggested that the command structure be allocated in cache-

inhibited memory.