CS8900A
Crystal LAN™ ISA Ethernet Controller
Command
Opcode
(bits 9,8)
EEPROM Address Data
(bits 7 to 0)
EEPROM Type
Execution
Time
Read Register
Write Register
1,0
0,1
1.1
0,0
word address
word address
word address
XX11-XXXX
11XX-XXXX
XX00-XXXX
00XX-XXXX
XX10-XXXX
10XX-XXXX
XX01-XXXX
01XX-XXXX
yes
yes
no
all
25 µs
10 ms
10 ms
9 µs
all
Erase Register
Erase/Write Enable
all
no
‘CS46, ‘C46
no
‘CS56, ‘C56, ‘CS66, ‘C66
‘CS46, ‘C46
9 µs
Erase/Write Disable
Erase-All Registers
Write-All Register
0,0
0,0
no
9 µs
no
‘CS56, ‘C56, ‘CS66, ‘C66
‘CS46, ‘C46
9 µs
0,0
0,0
no
10 ms
9 µs
no
‘CS56, ‘C56, ‘CS66, ‘C66
‘CS46, ‘C46
0,0
0,0
yes
yes
10 ms
10 ms
‘CS56, ‘C56, ‘CS66, ‘C66
Table 7. EEPROM Commands
location is written into the EEPROM Data register.
If the command is an Erase or Erase-All, no data is FFh to the specified EEPROM location. During the
transferred to or from the EEPROM Data register. Erase-All command, the CS8900A writes FFh to
During the Erase command, the CS8900A writes
Before issuing any command, the host must wait all locations.
for the SIBUSY bit (Register 16, SelfST, bit 8) to
3.6 Boot PROM Operation
clear. After each command has been issued, the
host must wait again for SIBUSY to clear.
The CS8900A supports an optional Boot PROM
used to store code for remote booting from a net-
work server.
3.5.3 Enabling Access to the EEPROM
The Erase/Write Enable command provides protec-
tion from accidental writes to the EEPROM. The
host must write an Erase/Write Enable command
before it attempts to write to or erase any EEPROM
memory location. Once the host has finished alter-
ing the contents of the EEPROM, it must write an
Erase/Write Disable command to prevent unwant-
ed modification of the EEPROM.
3.6.1 Accessing the Boot PROM
To retrieve the data stored in the Boot PROM, the
host issues a Read command to the Boot PROM as
a Memory space access. The CS8900A decodes the
command and drives the CSOUT pin low, causing
the data stored in the Boot PROM to be shifted into
the bus transceiver. The bus transceiver then drives
the data out onto the ISA bus.
3.5.4 Writing and Erasing the EEPROM
3.6.2 Configuring the CS8900A for Boot PROM
Operation
To write data to the EEPROM, the host must exe-
cute the following series of commands:
Figure 6 shows how the CS8900A should be con-
nected to the Boot PROM and ’245 driver. To con-
figure the CS8900A’s internal registers for Boot
PROM operation, the Boot PROM Base Address
must be loaded into the Boot PROM Base Address
register (PacketPage base + 0030h) and the Boot
PROM Address Mask must be loaded into the
1) Issue an Erase/Write Enable command.
2) Load the data into the EEPROM Data register.
3) Issue a Write command.
4) Issue an Erase/Write Disable command.
CIRRUS LOGIC PRODUCT DATA SHEET
DS271PP3
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