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Format of Device Descriptor Table (DDT)

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Offset Size Description

00h

BYTE

bits 7 - 4 : reserved (set to 0)
bits 3 - 0 : slot of device (0 = system board)

01h

BYTE

bits 7 - 4 : second interrupt for this device (0 = none)
bits 3 - 0 : first interrupt for this device (0 = none)

02h

BYTE

bits 7 - 4 : second arbitration level for this device
bits 3 - 0 : first arbitration level for this device

03h

WORD

DDT indicators (see #00536)

05h

BYTE

reserved (0)

06h

WORD

device ID (0 = none)

08h

WORD

starting address of first I/O block (0 = none)

0Ah

WORD

starting address of second I/O block (0 = none)

OCh

WORD

starting address of third I/O block (0 = none)

OEh

DWORD

start of first non-system memory block (0 = none)

12h

WORD

size of first non-system memory block (in kilobytes)

14h

DWORD

start of second non-system memory block (0 = none)

18h

WORD

size of second non-system memory block (in kilobytes)

1Ah

BYTE

implementation identifier of the device

1Bh

BYTE

implementation revision level of the device

Note:

I/O block addresses and non-system memory addresses are listed in ascending order in each DDT entry.