Plug and Play BIOS Specification

Plug and Play BIOS Specification 1.0A Page 29
1. The Plug and Play Structure is valid.
2. Any calls made to the Plug and Play BIOS functions will either perform the function as
described by Version 1.0 of this specification or return the FUNCTION_NOT_SUPPORTED error
code. Plug and Play compliant systems are required to provide the support as outlined in the table
below.
3. All of the runtime Plug and Play services will be contained in a contiguous 64K code segment.
Presence of the $PnP structure in the system BIOS does not mean that the system is fully Plug and Play
compliant. For instance, a system BIOS could have a valid $PnP structure; yet, return
FUNCTION_NOT_SUPPORTED for each of the functions described in this specification. The following
table specifies the required Plug and Play BIOS support necessary for systems with different
characteristics to meet full Plug and Play compliance.
System Characteristics Required Functions Optional Functions
Systems with embedded devices on the systemboard.
Proprietary bus devices or local ISA devices on the
systemboard.
00h, 01h, 02h
Systems that support docking to expansion bases 03h, 04h, 05h
Reserved 06h, 07h, 08h
Systems with an ISA expansion bus 40h 09h, 0Ah
ESCD Interface Functions 41h, 42h, 43h
Systems supporting APM 1.1 (and greater) 0Bh
*Note:
Functions 09h, 0Ah, and 40h are designed to support systems with an ISA Expansion bus. The
information which must be stored in nonvolatile media is the information concerning the resources
allocated to static legacy ISA devices. If functions 09h and 0Ah designate that the system implementation
utilizes the ESCD for storing static resource allocation, then the caller should utilize the interface defined
by the ESCD Specification to report statically allocated resources. Functions 41h, 42h, and 43h defined in
section 4.7 specify the ESCD interface. Refer to the ESCD Specification for a complete description of the
interfaces to support the ESCD as well as the format of the ESCD. BIOS support of these functions is
optional.Systems with an ISA Expansion bus may provide these BIOS functions to enhance the Plug and
Play BIOS POST process for assigning a conflict free configuration to the required boot devices.
The following table provides some examples of systems with certain characteristics and categorically lists
the functions that would be required to be Plug and Play compliant.