
RTL8305SB
2002/04/09
16
Rev.1.0
5.7 Reserved Pins
Pin Name
RESERVED1
5.8 Serial EEPROM and SMI Pins
Pin No. Type
72
Description
Reserved:
Reserved pin for internal use. Should be left floating.
Default
1
I/O
The serial EEPROM and external device should be 2.5V compatible, as the output of the RTL8305SB is 2.5V.
If the external device output is 3.3V. There are 0.7V (3.3V–2.5V) on pull-high resistors which one side is a 3.3V external
device and the other side is 2.5V VDD. There are 0.7V (3.3V–2.5V) on pull-high resistors which one side is 3.3V VDD and
the other side is the 2.5V output of the RTL8305SB.
Pin Name
Pin No. Type
Description
EnEEPROM
73
I
Enable EEPROM:
This pin sets the RTL8305SB to enable the loading
of the serial EEPROM upon reset.
1: Enable
0: Disable
8305SB = EnEEPROM, 8305S = NC.
SCL_MDC
74
I/O
SCL or MDC:
This pin is tri state when pin RESET#=0.
When pin EnEEPROM=1, this pin becomes SCL (output) to load the serial
EEPROM upon reset. Then this pin changes as MDC (input) after reset. In
this case, this pin should be pulled-high (2.5V) by an external resistor.
When pin EnEEPROM=0, this pin is MDC (input): 0 to 25MHz clock,
sourced by an external device to sample MDIO. In this case, if, and only
if, this pin is floating, it needs an external pull-high (2.5V) resistor.
Because this pin can be connected to a 2.5V or 3.3V device, this pin has
no internal pull-high resistor.
8305SB = SCL_MDC, 8305S = NC.
SDA_MDIO
75
IO
SDA or MDIO:
This pin is tri state when RESET#=0.
When pin EnEEPROM=1, this pin becomes SDA (input/output) to load
the serial EEPROM upon reset. Then this pin changes as MDIO
(input/output) after reset.
When pin EnEEPROM=0, this pin is MDIO (input/output).
It should be pulled-high by an external resistor.
Because this pin can be connected to a 2.5V or 3.3V device, this pin has
no internal pull-high resistor.
8305SB = SDA_MDIO, 8305S = NC.
Default
1