
LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
Datasheet 
Document Number: 249241
Revision Number: 007
Revision Date: August 28, 2003
113
K8
AMDIX_EN
I, ST, IP
Auto MDI/MDIX Enable Default.   
This pin is read at startup or reset. Its value at that time is 
used to set the default state of Register bit 27.9 for all ports. 
These register bits can be read and overwritten after 
startup / reset. Refer to 
Table 40 on page 119
.
When active (High), automatic MDI crossover (MDIX) 
(regardless of segmentation) is selected for all ports. When 
inactive (Low) MDIX is selected according to the MDIX pin.
M10,
L9,
M9
CFG_1
CFG_2
CFG_3
I, ST, ID
Global Port Configuration Defaults 1-3.
These pins are read at startup or reset. Their value at that 
time is used to set the default state of register bits shown in 
Table 42, “Intel LXT9785/9785E Global Hardware 
Configuration Settings” on page 129
 for all ports. These 
register bits can be read and overwritten after startup / 
reset. 
When operating in Hardware Control Mode, these pins 
provide configuration control options for all the ports (refer 
to 
page 129
 for details).
C1,
F1
FIFOSEL1
FIFOSEL0
I, ID, ST
FIFO Select <1:0>.
These pins are read at startup or reset. Their value at that 
time is used to set the default state of Register bits 
18.15:14 for all ports. These register bits can be read and 
overwritten after startup/reset.
These pins are shared with RMII-RxER<5:4>. An external 
pull-up resistor (see applications section for value) can be 
used to set FIFO Select<1:0> to active while RxER<5:4> 
are three-stated during hardware reset. If no pull-up is 
used, the default FIFO select state is set via the internal 
pull-down resistors. 
See 
Table 36, “Intel LXT9785/LXT9785E Receive FIFO 
Depth Configurations” on page 97
.
B3
LINKHOLD
I, ID, ST
LINKHOLD Defaul
t. This pin is read at startup or reset. Its 
value at that time is used to set the default state of Register 
bit 0.11 for all ports. This register bit can be read and 
overwritten after startup / reset. When High, the LXT9785/
9785E powers down all ports. 
This pin is shared with RMII-RxER6. An external pull-up 
resistor (see applications section for value) can be used to 
set LINKHOLD active while RxER6 is three-stated during 
H/W reset. If no pull-up is used, the default LINKHOLD 
state is set inactive via the internal pull-down resistor. 
LED Signal Descriptions
N9,
P9
LED0_1
LED0_2
OD, TS, 
SL, IP
Port 0 LED Drivers 1-2.
These pins drive LED indicators for Port 0. Each LED can 
display one of several available status conditions as 
selected by the LED Configuration Register (refer to 
Table 96, “LED Configuration Register (Address 20, Hex 
14)” on page 213
 for details).
Table 39. Intel
 LXT9785 BGA15 Signal Descriptions  (Sheet 5 of 7)
BGA15 Ball 
Designation
Symbol
Type
Signal Description
1. Type Column Coding: I = Input, O = Output, OD = Open Drain output, ST = Schmitt Triggered input, TS = 
Three-State-able output, SL = Slew-rate Limited output, IP = weak Internal Pull-up, ID = weak Internal pull-
Down.