Microsoft Debug Port Table 2 (DBG2) - 1

Microsoft Debug Port Table 2 (DBG2)

December 10,, 2015

Abstract

This specification defines the format of the Debug Port Table 2 (DBG2), used in platform firmware to describe the debug ports available on the system.

This information applies to the following operating systems:

The next version of Windows, code-named Windows8

References and resources discussed here are listed at the end of this paper.

The current version of this paper is maintained on the web at:
Microsoft Debug Port Table 2 (

Patent Notice:

Microsoft is making certain patent rights available for implementations of this specification under two options:

1) Microsoft’s Community Promise, available at ; or

2) The Open Web Foundation Final Specification Agreement Version 1.0 ("OWF 1.0") as of October 1, 2012, available at .

Document History

Date / Change
November 29, 2011 / First publication.
May 22, 2012 / Updates to Table 3 per final supported platforms for Windows 8.
August 10, 2015 / Updated patent notice.
October 6, 2015 / Added new serial debugging subtypes (ARM SBSA UART, ARM DCC)
December 10, 2015 / Added new serial debugging subtype (BCM2835)

Contents

Introduction

Debug Port Table 2 (DBG2)

Debug Device Information structure

Resources

Introduction

Microsoft requires a debug port on all systems. To describe the debug port(s) available on a platform, Microsoft defines an operating system–specific table (DBG2). This table specifies one or more independent ports for debugging purposes. The presence of adebug port table indicates that the system includes a debug port. The tablecontains information about the configuration of the debug port. The table is located in system memory with other Advanced Configuration and Power Interface (ACPI) tables, and must be referenced in the ACPI Root System Description Table (RSDT).

The DBG2 table replaces the ACPI Debug Port Table (DBGP) on platforms whose debug port implementations cannot be described using DBGP.

Debug Port Table 2 (DBG2)

Table 1 defines the fields in DBG2.

Table 1. Debug Port Table 2 format

Field / Byte length / Byte offset / Description
Header
Signature / 4 / 0 / ‘DBG2’. Signature for Debug Port Table 2.
Length / 4 / 4 / Length, in bytes, of the entire Debug Port Table 2.
Revision / 1 / 8 / For this version of the specification, this value is 0.
Checksum / 1 / 9 / Entire table must sum to zero.
OEM ID / 6 / 10 / Original equipment manufacturer (OEM) ID.
OEM TableID / 8 / 16 / For Debug Port Table 2, the table ID is the manufacturer model ID.
OEM Revision / 4 / 24 / OEM revision of Debug Port Table 2 for the supplied OEM Table ID.
Creator ID / 4 / 28 / Vendor ID of utility that created the table.
Creator Revision / 4 / 32 / Revision of utility that created the table.
OffsetDbgDeviceInfo / 4 / 36 / Offset, in bytes,from the beginning of this table to the first Debug Device Information structure entry.
NumberDbgDeviceInfo / 4 / 40 / Indicates the number of Debug Device Information structure entries.
Debug Device Information Structure[NumberDbgDeviceInfo] / Variable / OffsetDbgDeviceInfo / A list of Debug Device Information structures for this platform. The structure format is defined in the Debug Device Information structure section, later in this document.

Debug Device Information structure

Table 2. Debug Device Information structure format

Field / Byte length / Byte offset / Description
Revision / 1 / 0 / Revision of the Debug Device Information structure. For this version of the specification, this must be 0.
Length / 2 / 1 / Length, in bytes, of this structure, including NamespaceString and OEMData.
NumberofGenericAddressRegisters / 1 / 3 / Number of generic address registers in use.
NameSpaceStringLength / 2 / 4 / Length, in bytes, of NamespaceString, including null characters.
NameSpaceStringOffset / 2 / 6 / Offset, in bytes, from the beginning of this structure to the field NamespaceString[]. This value mustbe validbecause this string must be present.
OemDataLength / 2 / 8 / Length, in bytes, of the OEM data block.
OemDataOffset / 2 / 10 / Offset, in bytes, to the field OemData[] from the beginning of this structure. This value will be 0 if no OEM data is present.
Port Type / 2 / 12 / Debug port type for this debug device. Each of these values will have a corresponding subtype value as shown in Table 3.
Port Subtype / 2 / 14 / Debug port subtype for this debug device. See Table 3.
Reserved / 2 / 16 / Reserved, must be 0.
BaseAddressRegisterOffset / 2 / 18 / Offset, in bytes, from beginning of this structure to the field BaseaddressRegister[].
AddressSizeOffset / 2 / 20 / Offset, in bytes, from beginning of this structure to the field AddressSize[].
BaseAddressRegister[] / (NumberofGenericAddressRegisters) * 12 / BaseAddressRegisterOffset / Array of generic addresses.
AddressSize[] / (NumberofGenericAddressRegisters) * 4 / AddressSizeOffset / Array of address sizes corresponding to each generic address above.
NamespaceString[] / NameSpaceStringSize / NameSpaceStringOffset / Null-terminated ASCII string to uniquely identify this device. This string consists of a fully qualified reference to the object that represents this device in the ACPI namespace. If no namespace device exists, NamespaceString[] must contain a period “.”.
OemData[] / OemDataLength / OemDataOffset / Optional, variable-lengthOEM-specific data.

Table 3. Debug port types and subtypes

Port / Type / Subtype / Description
Reserved / 0x0000 - 0x7FFF and0xFFFF / All / Reserved (Do Not Use)
Serial / 0x8000 / 0x0000 / Fully 16550-compatible
0x0001 / 16550 subset compatible with DBGP Revision 1
0x0002 / Reserved (Do Not Use)
0x0003 / ARM PL011 UART
0x0004 – 0x000c / Reserved (Do Not Use)
0x000d / (deprecated) ARM SBSA (2.x only) Generic UART supporting only 32-bit accesses
0x000e / ARM SBSA Generic UART
0x000f / ARM DCC
0x0010 / BCM2835
1394 / 0x8001 / 0x0000 / IEEE1394 Standard Host Controller Interface
0x0001 – 0xFFFF / Reserved (For Future Use)
USB / 0x8002 / 0x0000 / XHCI-compliant controller with debug interface
0x0001 / EHCI-compliant controller with debug interface
0x0002 -0x0006 / Reserved (Do Not Use)
0x0007 – 0xFFFF / Reserved (For Future Use)
Net / 0x8003 / NNNN / NNNN must be a valid PCI-assigned Vendor ID
0x8004 / All / Reserved (Do Not Use)
Reserved / 0x8005 – 0xFFFE / All / Reserved (For Future Use)

Resources

ACPI Specification