Crystal LAN CS8920, Техническое справочное руководство, Страница: 47 / 67

AN84REV1 47
CS8920 Technical Reference Manual
3.4.1 Serial Identifier
The Serial Identifier block is used to isolate
each individual ISA adapter in the system
during the PnP isolation sequence. The
Plug and Play ISA Specification defines the
Serial Identifier as consisting of a 32-bit
Vendor ID in compressed ASCII format
(typically the OEM’s EISA ID), a 32-bit
unique serial number and an 8-bit LFSR
checksum calculated on the Vendor ID and
serial number. Refer to Section 6.1 of the
Plug and Play ISA Specification 1.0a for
more information on the definition of the
Serial Identifier.
The Serial Identifier of each ISA adapter
must be unique. It is the responsibility of
the OEM to ensure that each adapter using
the same Vendor ID (EISA ID) is assigned
a unique serial number.
Note: All adapters using Crystal
Semiconductor’s EISA ID of “CSC” for
bytes 0 and 1 of the Vendor ID must set bit
6 of byte three to a 1 and bit 5 of byte three
to 0 (i. e., byte 3 must be X10X XXXX
where X is a don’t care).
Words 30h to 34h defined above in the
Driver Configuration Block are also used as
the PnP Serial Identifier. Refer to Figure
3.4.1 for an example of the Serial Identifier
Block
3.4.2 Resource Descriptors
Immediately following the Serial Identifier
are a series of data structures describing the
resource requirements of the adapter. The
format of this resource data for a typical
CS8920 ISA adapter is:
1. Plug and Play version number
2. Identifier String (variable length)
3. Logical Device ID
•
Resource descriptors (as needed)
•
IRQ
•
IO Ports
•
Memory Descriptor 0
•
Memory Descriptor 1
•
DMA Channel
4. End Tag
The identifier string is a variable length
string of ASCII characters and is used by
the operating system when reporting
configuration and error messages.
Following the Identifier String is the
Logical Device ID. The Logical Device ID
is used by PnP to identify multiple logical
devices embedded in a single physical ISA
card. However, the CS8920 PnP interface
only supports one logical device.
For logical device 0 (the CS8920), a list of
resource descriptors specify the ISA
resources required by the CS8920 (e.g.
DMA channel, IRQ, etc.) along with
acceptable values for each resource. The
order in which the resource descriptors are
listed is not important. Refer to the CS8920
Data Sheet for the acceptable ISA resources
for the CS8920.
The PnP configuration process will attempt
to reserve and assign available ISA
resources for all resource descriptors
specified in the resource descriptor list,
regardless of whether or not the resource is