AL103 Revision 1.0
3.14.4 Read Cycle Operation
Read operations are initiated in the same manner as write operations, with the exception that the R/
W bit of the EEPROM address is set to a “1.”
Device
Device
Start
Start
Address
Stop
Address
A
A
A
A
A
A
S
S
8-Bit Word Address
S
8-Bit Data n
EEDIO
Acknowledge
Acknowledge
No Acknowledge
Acknowledge
Figure 7
EEPROM Read Cycle
3.14.5 Reprogramming the EEPROM Configuration
There are two ways that the system can be reconfigured. Figure 8 shows an application using the
parallel interface to reprogram the EEPROM. In this application, the parallel port holds the reset
pins low, which forces the EEDIO pins to go into high impedance. Once the pins are in high
impedance, the EEPROM can now be programmed by the parallel port. Once the parallel port
releases the reset pins, the devices will start to download the EEPROM data and reconfigure the
devices.
An alternate way of reconfiguring the system is to directly change the register settings of the
AL103. After initialization, the EEPROM interface can act as a virtual EEPROM. In order for this
method to work, the EEPROM’s device address must be 000, while the AL103’s address will be
100. The customer can now program the AL103 as an EEPROM. The read and write timing is the
same as an EEPROM.
Because you read as well as write to the AL103, the registers status can be read from the AL103.
This will serve as a very useful tool for diagnostic of an unmanaged switch.
9/00
Reference Only / Allayer Communications
31
ABC [ ABC Taiwan Electronics Corp ]
