w89c840af Winbond Electronics Corp America, w89c840af Datasheet - Page 27

• Manufacturer Part Number: w89c840af
• Description: 100/10mbps Ethernet Controller
• Manufacturer: Winbond Electronics Corp America

depending on the configuration of C48/CBRCR. The relationship between the return value from the register
F30/FERBA and the setting to the register C48/CBRCR is described as the following table.
large the memory space is required and then write the memory space base address back to the register
F30/FERBA. In the cases of no boot ROM, the system BIOS will write back all 0 back into F30/FERBA.
the bit 0 of F30/FERBA and the bit 1 of F04/FCS are set to high at the same time. the on-board boot ROM data
will be fetched by W89C840AF and loaded into the host memory. On the other hand , the address decoder will
be disabled if the bit 0 of F30/FERBA is reset to 0. Under this case, W89C840AF will ignore the C48/CBRCR,
no matter what content it has.
power-on reset, the W89C840AF also provides another access way for the application program to do some
unusual applications, like down loading the ROM code or re-programming the ROM code on line.
No boot ROM
No boot ROM
8 Kbytes ROM
16 Kbytes ROM
32 Kbytes ROM
64 Kbytes ROM
128 Kbytes ROM
256 Kbytes ROM
According to the return value from the register F30/FERBA, The system BIOS can determine how
The address decoder of W89C840AF for accessing the on-board ROM memory will be enabled if both
Usually, the on-board boot ROM data can be read by the system BIOS during host system booting or
The procedures for on-line reading the on-board ROM device are described as following.
1) write the offset address into the C28/CBROA.
2) reset the bit 11 of C24/CMIIR to 0.
3) set the bit 14 of C24/CMIIR to 1.
4) read back the data form C24/CMIIR
The procedures for on-line writing the on-board ROM device are described as following
1) write the offset address into the C28/CBROA.
2) reset the bit 11 of C24/CMIIR to 0.
3) write the one byte data into C24/CMIIR bit 0 to bit 7.
4) set the bit 13 of C24/CMIIR to 1.
ROM size
C48/CBRCR configuration
00000000H
00000001H
00000002H
00000003H
00000004H
00000005H
00000006H
00000007H
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Publication Release Date:October 2000
Revision 1.01
F30/FERBA return value
FFFFE001H
FFFFC001H
FFFC0001H
FFFF8001H
FFFF0001H
FFFE0001H
00000000H
00000000H
W89C840AF