
LXT9785 and LXT9785E Advanced 8-Port 10/100 Mbps PHY Transceivers
40
Datasheet 
Document Number: 249241
Revision Number: 007
Revision Date: August 28, 2003
Table 8. Intel
 LXT9785/LXT9785E SS-SMII Specific Signal Descriptions – PQFP
Designation
Symbol
Type
1
Signal Description
2,3
PQFP
PBGA
35
204
A6,
C16
TxSYNC0
TxSYNC1
I, ID
SS-SMII Transmit Synchronization.
The MAC must generate a TxSYNC pulse every 10 TxCLK 
cycles to mark the start of TxData segments. TxSYNC0 is 
used when 1x8 port sectionalization is selected.
58
17
E4,
B12
RxSYNC0
RxSYNC1
O, TS,
ID
SS-SMII Receive Synchronization.
The LXT9785/9785E generates these pulses every 10 
RxCLK cycles to mark the start of RxData segments for the 
MAC. RxSYNC1 is used when 1x8 port sectionalization is 
selected. RxSYNC0 may not be used. These outputs are 
only enabled when SS-SMII mode is enabled.
32
201
C8,
D17
TxCLK0
TxCLK1
I, ID
SS-SMII Transmit Clock.
The MAC sources this 125 MHz clock as the timing 
reference for TxData and TxSYNC. Only TxCLK0 is used 
when 1x8 port sectionalization is selected. 
See “Clock/
SYNC Requirements” on page 125
for detailed clock 
requirements.
60
21
E3,
B11
RxCLK0
RxCLK1
O, TS,
ID
SS-SMII Receive Clock.
The LXT9785/9785E generates these clocks, based on 
REFCLK, to provide a timing reference for RxData and 
RxSYNC to the MAC. RxCLK1 is used when 1x8 port 
sectionalization is selected. RxCLK0 may not be used. 
See 
“Clock/SYNC Requirements” on page 125 
for detailed clock 
requirements
.
 These outputs are only enabled when SS-
SMII mode is enabled. 
54
45
36
27
15
7
205
197
B1,
B4,
C7,
B9,
C12,
B15,
B17,
F14
RxData1
RxData2
RxData3
RxData4
RxData5
RxData6
RxData7
O, TS,
ID
Receive Data - Ports 0-7.
These serial output streams provide data received from 
the network. The LXT9785/9785E drives the data out 
synchronously to REFCLK.
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 H/W Power-Down mode.   If a Pin is an output or an I/O, the IP/ID 
resistors are also disabled when the output is enabled.
3. RxData[0:7], RxSYNC[0:1], and RxCLK[0:1] outputs are three-stated in Isolation and H/W Power-Down 
modes and during H/W reset.