XR72L52 Datasheet, PDF (370/480 Pages) Exar Corporation – TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER

XRT72L52
REV. 1.0.1
xr
TWO CHANNEL DS3/E3 FRAMER IC WITH HDLC CONTROLLER
A. Local Timed - Uses the TxInClk signal as the Timing Reference
In this mode, the Transmit Section of the XRT72L52 will use the TxInClk signal as its timing reference.
B. Serial Mode
The XRT72L52 will receive the E3 payload data, in a serial manner, via the TxSer input pin. The Transmit Pay-
load Data Input Interface (within the XRT72L52) will latch this data into its circuitry, on the rising edge of the Tx-
InClk input clock signal.
C. Delineation of Outbound E3 frames (Frame Master Mode)
The Transmit Section of the XRT72L52 will use the TxInClk signal as its timing reference, and will initiate E3
frame generation, asynchronously with respect to any externally applied signal. The XRT72L52 will pulse its
TxFrame output pin "High" whenever it is processing the very last bit-field within a given E3 frame.
D. Sampling of payload data, from the Terminal Equipment
In Mode 3, the XRT72L52 will sample the data, at the TxSer input pin, on the rising edge of TxInClk.
Interfacing the Transmit Payload Data Input Interface block of the XRT72L52 to the Terminal Equipment
for Mode 3 Operation
Figure 149 presents an illustration of the Transmit Payload Data Input Interface block (within the XRT72L52)
being interfaced to the Terminal Equipment, for Mode 3 operation.
FIGURE 149. THE TERMINAL EQUIPMENT BEING INTERFACED TO THE TRANSMIT PAYLOAD DATA INPUT INTERFACE
BLOCK FOR MODE 3 (SERIAL/LOCAL-TIMED/FRAME-MASTER) OPERATION
3 4.368M H z
Clock Source
E 3 _ C lo c k _ In
E 3_D ata_O ut
T x_S tart_of_F ram e
E 3_O v erhead_Ind
T x In C lk
TxSer
T xF ram e
T x O H _Ind
N ib In tf
Term inal Equipm ent
E3 Fram er
Mode 3 Operation of the Terminal Equipment
In Figure 149, both the Terminal Equipment and the XRT72L52 are driven by an external 34.368 MHz clock
signal. This clock signal is connected to the E3_Clock_In input of the Terminal Equipment and the TxInClk in-
put pin of the XRT72L52.
The Terminal Equipment will serially output the payload data on its E3_Data_Out output pin, upon the rising
edge of the signal at the E3_Clock_In input pin. Similarly, the XRT72L52 will latch the data, residing on the Tx-
Ser input pin, on the rising edge of TxInClk.
The XRT72L52 will pulse the TxFrame output pin "High" for one bit-period, coincident while it is processing the
last bit-field within a given Outbound E3 frame. The Terminal Equipment is expected to monitor the TxFrame
signal (from the XRT72L52) and to place the first bit, within the very next Outbound E3 frame on the TxSer in-
put pin.
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