Filter
Top Products
48 Intel 8255x 10/100 Mbps Ethernet Controller Family Open Source Software Developer Manual
Host Software Interface
6.3.4.3 Software Read Access from the EEPROM
To read from the EEPROM, software is required to perform the following steps. The example is a
read from address 02h (0000 0010b).
Note: Since the address field is written most significant bit first, software must know the address field
size prior to starting a read or write access.
1. Activate the EEPROM by writing a 1 to the EECS bit.
2. Write the read opcode, including the start bit (110b), one bit at a time, starting with the most
significant bit (1):
a. Write the opcode bit to the EEDI bit.
b. Write a 1 to EESK bit then wait the minimum SK high time.
c. Write a 0 to EESK bit then wait the minimum SK low time.
d. Repeat steps 2.a through 2.c for the next two opcode bits.
3. Write the address field, one bit at a time, starting with the most significant bit.
a. Write the address bit to the EEDI bit.
b. Write a 1 to EESK bit then wait the minimum SK high time.
c. Write a 0 to EESK bit then wait the minimum SK low time.
d. Read the EEDO bit (looking for the dummy 0 bit).
e. Repeat steps 3.a through 3.d until the EEDO bit equals 0, indicating that the address field
has been completely written.
4. Read a 16-bit word from the EEPROM, one bit at a time, starting with the most significant bit.
a. Write a 1 to the EESK bit then wait the minimum SK high time.
b. Read a data bit from the EEDO bit.
c. Write a 0 to the EESK bit then wait the minimum SK low time.
d. Repeat steps 4.a through 4.d an additional 15 times.
5. De-activate the EEPROM by writing a 0 to the EECS bit.
Figure 13. EEPROM Read Timing Diagram
A
1
A
0
EECS
EESK
EEDI
EEDO
A
5
A
4
A
2
D
15
D
0
READ OP code
A
3
A
1
A
0