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XRT7250
DS3/E3 FRAMER IC
REV. 1.1.1
341
How to configure the XRT7250 into the Serial/
Loop-Timed/Non-Overhead Interface Mode
1. Set the NibIntf input pin "Low".
2. Set the TimRefSel[1:0] bit fields (within the
Framer Operating Mode Register) to "00" as illus-
trated below.
3. Interface the XRT7250, to the Terminal Equip-
6.2.1.2
Mode 2 - The Serial/Local-Timed/
Frame-Slave Mode Behavior of the XRT7250
If the XRT7250 has been configured to operate in this
mode, then the XRT7250 will function as follows.
A. Local Timing - Uses the TxInClk signal as the
Timing Reference
In this mode, the Transmit Section of the XRT7250
will use the TxInClk signal as its timing reference.
B. Serial Mode
The XRT7250 will receive the E3 payload data, in a
serial manner, via the TxSer input pin. The Transmit
Payload Data Input Interface (within the XRT7250)
will latch this data into its circuitry, on the rising edge
of the TxInClk input clock signal.
C. Delineation of Outbound E3 frames (Frame
Slave Mode)
The Transmit Section of the XRT7250 will use the Tx-
InClk input as its timing reference, and will use the
FIGURE 158. BEHAVIOR OF THE TERMINAL INTERFACE SIGNALS BETWEEN THE TRANSMIT PAYLOAD DATA INPUT
INTERFACE BLOCK OF THE XRT7250 AND THE TERMINAL EQUIPMENT (FOR MODE 1 OPERATION)
Terminal Equipment Signals
E3_Clock_In
E3_Data_Out
Tx_Start_of_Frame
E3_Overhead_Ind
XRT7250 Transmit Payload Data I/F Signals
RxOutClk
TxSer
TxFrame
TxOH_Ind
Payload[4238]
Payload[4239]
FA1, Bit 7
FA1, Bit 6
Payload[4238]
Payload[4239]
FA1, Bit 7
FA1, Bit 6
Note: The FA1 byte will not be processed by the
Transmit Payload Data Input Interface.
E3 Frame Number N
E3 Frame Number N + 1
Note: RxFrame pulses high to denote
E3 Frame Boundary.
Note: TxOH_Ind pulses high for
16 bit periods in order to
denote Overhead Data
(e.g., the FA1 and FA2 bytes)
FRAMER OPERATING MODE REGISTER (ADDRESS = 0X00)
BIT 7BIT 6BIT 5BIT 4BIT 3BIT2
BIT 1
BIT 0
Local Loopback
DS3/E3*
Internal LOS
Enable
RESET
Interrupt
Enable Reset
Frame Format
TimRefSel[1:0]
R/W
00
1
0
1
0