IBM 770 manual Image, B-4 SMAPI BIOS

Header

Image

Systems

that

support

SMAPI

BIOS must provide the following header

image in the F000 segment system ROM area at the 16-byte

boundary. The

client

needs

to search and find this SMAPI

BIOS

header image

to

get

the

entry

point for

the

service.

Field

Offset

Length

Value

(in

Hex)

Signature

00

4 bytes

'$SMB

'

(ASCII)

Version

(Major)

04

Byte

01h

Version

(Minor)

05

Byte

00h

Length

06

Byte

20h

Checksum

07

Byte

–

Information

Word

08

Word

–

Reserved

1

0A

Word

–

Real mode 16-bit offset

to0C

entry

Word

–

point

Real mode 16-bit code

segment0E

Word

–

address

Reserved

2

10

Word

–

16-bit protected mode offset12

to

Word

–

entry

point

16-bit protected mode code14

Double

–

segment

base address

words

32-bit protected mode offset18

to

Double

–

entry

point

words

32-bit protected mode code1C

Double

–

segment

base address

words

Signature

ASCII Code'$SMB

'

is

stored

at

the top

of

the

header

image.

Version

(Major

or

Minor)

Indicates

the

SMAPI

BIOS

version.

Length

The

length

of

the

header

image.

Checksum

Checksum

byte

area. The

client

verifies that this

header

image

is

valid by using this checksum; the client

should

check

all

header

image

bytes,

and

the

result will

be

zero

bytes.

B-4 SMAPI BIOS