Datasheet

____________________________________________________ DS34T101, DS34T102, DS34T104, DS34T108
30 of 366
Note 1: In pin names, the suffix “n” stands for port number: n=1 to 8 for DS34T108; n=1 to 4 for DS34T104; n=2 for DS34T102; n=1 for
DS34T101. All pin names ending in “_N” are active low.
Note 2: All pins, except power and analog pins, are CMOS/TTL unless otherwise specified in the pin description.
PIN TYPES
I = input pin
I
A
= analog input pin
I
PD
= input pin with internal 50k pulldown to DVSS
I
PU
= input pin with internal 50k pullup to DVDDIO
IO = input/output pin
IO
PD
= input/output pin with internal 50k pulldown to DVSS
IO
PU
= input/output pin with internal 50k pullup to DVDDIO
O = output pin
O
A
= analog output pin
O
Z
= output pin that can be placed in a high-impedance state
P = power-supply or ground pin
9.2 Detailed Pin Descriptions
Table 9-2. Internal E1/T1 LIU Line Interface Pins
PIN NAME
(1)
TYPE
(2)
PIN DESCRIPTION
TXENABLE I LIU Transmit Enable Input (for All LIUs)
0 = All LIU transmitter outputs TTIPn and TRINGn are disabled (high-impedance)
1 = LIU transmitter outputs TTIPn and TRINGn are enabled/disabled by register fields
Registers fields LMCR:TX
EN (transmit enable) and LMCR:TPDE (transmit power
down) affect the state of TTIPn and TRINGn on a per-port basis when TXENABLE=1.
TTIPn, TRINGn Oa
LIU Transmitter Analog Outputs
The LIU transmitter drives outgoing T1, E1 and J1 physical layer signals on
TTIP/TRING differential pairs. The LIU transmitter can provide internal impedance
matching for E1 75 ohms, E1 120 ohms, T1 100 ohms or J1 110 ohms. All LIU
TTIP/TRING pairs are disabled (high-impedance) when the TXENABLE pin is low.
Registers fields LMCR:TX
EN (transmit enable) and LMCR:TPDE (transmit power
down enable) affect the state of TTIP/TRING on a per-port basis when TXENABLE=1.
RTIPn, RRINGn Ia
LIU Receiver Analog Inputs
The LIU receiver accepts incoming T1, E1 and J1 physical layer signals on the
RTIP/RRING differential pair. The LIU receiver can provide internal impedance
matching for E1 75 ohms, E1 120 ohms, T1 100 ohms or J1 110 ohms or can work
with external termination resistors. See the RXTSEL p
in description and section
10.13.3.1.
Regi
ster field LMCR.RP
DE can be used to power down LIU receivers on a per-port
basis. When RPDE=1, RTIP and RRING become high-impedance.
RXTSEL I Receive Termination Selection Input (for All LIUs)
This pin configures LIU receivers for internal or external line termination (impedance
matching). This pin only affects those LIUs where LTRCR:RHPM=1. In rec
eivers
where RHPM=0, LRISMR.RIMPON
controls internal vs. external impedance matching
on a per-port basis.
0= External termination
1 = Internal termination
RESREF I
Reference Resistor for LIU Analog Circuits
This pin must be tied to ARVSS through a 10k 1% resistor. The LIU transmitter and
receiver use this reference resistor to tune internal termination impedance and other
analog circuits. The resistor should be placed as close as possible to the device, and
capacitance on the RESREF node must be < 10pF.