XRT5794ES Datasheet, PDF (3/11 Pages) Exar Corporation – Evaluation System

XRT5794ES
Equipment-Side Signal Characteristics
All equipment-side connections at P1 and P2 are TTL
logic-level compatible for the inputs and outputs. Specific
signal types present at these pins are as follows.
LOS1 Through LOS4
These pins are the loss signal outputs (LOS) for the for
receive channels. A LOS output will go to a logic 1 state
when the input applied to the corresponding receiver is
less that the LOS threshold voltage.
RXPOS1 Through RXPOS4
The signal present at these pins is the positive half of the
dual-rail receive data. A positive bipolar input pulse at a
receiver input will produce a positive-going pulse at the
corresponding RXPOS output. Data pulse width at an
RXPOS output is approximately equal to the width of the
pulse applied to the reciever input at its 50% amplitude
point.
RXNEG1 Through RXNEG4
The signal present at these pins is the negative half of the
dual-rail receive data. A negative bipolar input pulse at a
receiver input will produce a positive-going pulse at the
corresponding RXNEG output. Data pulse width is the
same as described above for the RXPOS output.
TXCLK1 Through TXCLK4
These pins are the transmit clock inputs of four transmit
channels. For a specific channel, TXCLK is a 2.048 MHz
50% duty cycle square wave that is synchronized with the
data to be transmitted over that channel.
TXPOS1 Through TXPOS4
These pins are the positive rail inputs for the dual-rail
transmit data for the four tranmit channels. A
positive-going pulse at a TXPOS input will produce a
positive bipolar outout pulse at the corresponding
tranmitter output. The signal applied to a TXPOS input
must be wider that the positive half cycle of the
corresponding TXCLK, and must also meet the set-up
and hold time specified in the XR-T5794 datasheet. When
these conditions are met, the pulse width at the
transmitter output TXOUT is determined by the positive
going half-cycle of TXCLK .
TXNEG1 Through TXNEG4
These pins are the negative rail input for the dual-rail
transmit data for the four transmit channels. A
positive-going pulse at a TXNEG input will produce a
negative bipolar output pulse at the corresponding
transmitter output. The pulse width conditions described
above for the TXPOS input also apply to TXNEG.
Operation Without TXCLK
Operation without TXCLK is possible if this pin is
connected to either DGND or DVDD. Transmit output
pulse width in this mode of operation is determined by the
widths of the pulsed applied to the TXPOS and TXNEG
inputs. Therefore, the data applied to these inputs must
be one-half width return-to-zero (RZ) pulses in order to
produce a normal width bipolar transmit output pulse.
DIP Switch Settings
On the demo board, the logic levels presented at all
control-type XR-T5794 input pins may be set with DIP
switches. The following circuit is used to switch logic
levels. Each IC input that is to be programmed has a 10 K
W pull-up resistor connected to VDD. A SPAT DIP switch
section is also connected between this input and ground.
Therefore, when the switch lever is in the “ON” position as
marked on the switch body, the IC input is at a “Logic 0”
level. For convenience, a small “1” and “0” that indicate IC
pin logic level to switch position correspondence is
printed on the borad at the top end of each DIP switch.
Rev. 2.00
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