Crystal LAN CS8920, Technical Reference Manual, Page: 38 / 67

AN84REV1 38
CS8920 Technical Reference Manual
high byte of the word (bits 15-8). The
checksum value is the 2’s complement of
all the bytes in the Reset Configuration
Block excluding the checksum byte. (The
low byte of the checksum word is not used
and it is recommended that it be set to
0x00.) Since the checksum is the 2’s
complement of all the bytes in the Reset
Configuration Block, a total sum of 0
should result when the checksum value is
added to the sum of all the preceding bytes.
3.2.2 Typical Reset Blocks
The contents of the Reset Configuration
Block depend on the CS8920’s intended
mode of operation and adapter
configuration. Following are examples of
typical Reset Configuration Blocks for
three different modes of operation: as a
legacy adapter, as a PnP adapter, and as a
PnP adapter with the Auto-wakeup feature
enabled.
3.2.2.1 Recommended Reset
Configuration Block for a Legacy
Adapter
Table 3.2 shows the recommended Reset
Configuration Block for a CS8920 adapter
installed in a legacy system. The definition
of a legacy system as used in this chapter is
any PC system that does not rely on a
function of PnP to automatically configure
and activate the adapter.
The default state of the CS8920 after an
ISA reset is inactive with its IO base
address set to 0x00. Therefore, the adapter
must be activated and the IO base address
set from the EEPROM after each ISA reset.
Note: In systems that have an
autoconfiguring PnP BIOS but an ESCD
database is not maintained or the BIOS
does not activate the adapter, it will be
necessary to manually configure the
CS8920 as if in a legacy system. However,
it may still be advantageous to leave the
PnP functions of the CS8920 enabled.
Addr Word Description
00h B112h PnP Disabled, 18 bytes follow
01h 2158h 3 words, start with PacketPage 158h (IA)
02h 0100h Individual Address
03h 0302h of
04h 0504h 000102030405h
05h 0360h 1 word to PacketPage 360h (IO Base)
06h 0003h IO Base Address = 300h
07h 0330h 1 word to PacketPage 330h (RegActivate)
08h 0001h Activate Adapter
09h 2B00h Checksum of 20 bytes
Table 3.1. Reset Configuration Block
for Legacy System
This will allow the PnP BIOS or other
autoconfiguring components to be aware of
the CS8920 installed in the system and the
resources used by it. This will help insure
other PnP devices are not assigned
resources used by the CS8920. See section
3.4 for a discussion on manually
configuring the CS8920 using the PnP
resource tree.