
LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
92
Datasheet 
Document Number: 249241
Revision Number: 007
Revision Date: August 28, 2003
D2
59
MDIX
I, ID, ST
MDIX Select
Default.
This pin is read at startup or reset. Its value at that time 
is used to set the default state of Register bit 27.8 for 
all ports. These register bits can be read and 
overwritten after startup / reset.   Refer to 
Table 40 
“Intel LXT9785/LXT9785E MDIX Selection” on 
page 119
.
When AMDIX_EN is active this pin is ignored.
When AMDIX_EN is inactive, all ports are forced to the 
MDI or the MDIX function regardless of segmentation. 
If this pin is active (high), MDI crossover (MDIX) is 
selected. If this pin is inactive, non-crossover MDI 
mode is set.
This pin is shared with RMII-RxER0. An external pull-
up resistor (see applications section for value) can be 
used to set MDIX active while RxER0 is three-stated 
during H/W reset. If no pull-up is used, the default 
MDIX state is set inactive via the internal pull-down 
resistor. Do not tie this pin directly to VCCIO (vs. using 
a pull-up) in non-RMII modes.
L2,
L3,
M1
85
86
87
CFG_3
CFG_2
CFG_1
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 
Table 42 “Intel LXT9785/9785E Global 
Hardware Configuration Settings” on page 129
 for 
details).
M14
173
G_FX/TP
I, ST, ID
Global FX/TP 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 16.0 for 
all ports.   These register bits can be read and 
overwritten after startup / reset. Refer to
 Table 92 “Port 
Configuration Register (Address 16, Hex 10)” on page 207
.
This input selects whether all the ports are defaulted to 
TP vs. FX mode.
Table 32. Intel
 LXT9785/LXT9785E Miscellaneous Signal Descriptions – BGA23 (Sheet 3 of 4)
Ball/Pin 
Designation
Symbol
Type
1
Signal Description
2
BGA23
PQFP
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.
2. The IP/ID resistors are disabled during hardware power-down mode.