
XRT79L71
PRELIMINARY
87
1-CHANNEL DS3/E3 CLEAR-CHANNEL FRAMERLIU COMBO - CC/HDLC ARCHITECTURE
REV. P2.0.0
Configuring the XRT79L71 to operate in Mode 5 (Nibble-Parallel/Local-Timing/Frame-Slave Mode)
The user can configure the XRT79L71 to operate in Mode 5 by executing the following steps.
STEP 1 - Design your board such that the System-Side Terminal Equipment circuitry interfaces to the
Transmit Payload Data Input Interface in the manner as depicted above in Figure 38. STEP 2 - Configure the XRT79L71 to operate in the Nibble-Parallel Mode
This can be accomplished by setting the NibIntf input pin to a logic "High".
STEP 3 - Configure the XRT79L71 to operate in the Local-Timing/Frame Slave Mode
This can be accomplished by setting Bits 1 and 0 (TimRefSel[1:0]) within the Framer Operating Mode Register
to [0, 1] as depicted below.
4.2.1.6
Mode 6 - Nibble-Parallel/Local-Timing/Frame Master Mode Operation for the Transmit
Payload Data Input Interface Block
If the XRT79L71 is configured to operate in Mode 6 then all of the following is true.
FIGURE 39. AN ILLUSTRATION OF THE BEHAVIOR OF THE SYSTEM-SIDE TERMINAL EQUIPMENT SIGNALS FOR MODE
5 (NIBBLE-PARALLEL/LOCAL-TIMING/FRAME SLAVE) MODE OPERATION
Framer Operating Mode Register (Address = 0x1100)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Local Loop
Back
IsDS3
Internal LOS
Enable
RESET
Direct
Mapped
ATM
Frame For-
mat
TimRefSel[1:0]
R/W
0
1
0
1
0
1
System-Side Terminal Equipment Signals
XRT79L71 Transmit Payload Data Input Interface Signals
DS3 Frame Number N
DS3 Frame Number N + 1
Note: TxFrameRef is pulsed high to denote
first nibble within a new DS3 frame
TxInClk
Tx_Start_of_Frame
DS3_Nib_Clock_In
DS3_Data_Out[3:0]
Nibble [0]
Nibble [1]
TxInClk
TxFrameRef
TxNibClk
TxNib[3:0]
Nibble [0]
Nibble [1]
Nibble [1175]
Sampling Clock Edge
Of XRT79L71 Device