
XRT84L38
230
OCTAL T1/E1/J1 FRAMER
REV. 1.0.1
When the Receive Multiplex Enable bit is set to zero and the Receive Interface Mode Select [1:0] bits are set to
10, the Receive Back-plane interface of framer is running at a clock rate of 4.096MHz.
The interface consists of the following pins:
Data input (RxSer_n)
Receive Serial Clock Input signal (RxSerClk_n)
Receive Single-frame Synchronization Input signal (RxSync_n)
Receive Input Clock (RxInClk_n)
Receive Time-slot Indication clock (RxTSClk_n)
Receive Time Slot indicator bits (RxTSb[4:0]_n)
The Receive Back-plane interface is pumping out data through RxSer_n at an E1 equivalent data rate of
2.048Mbit/s. The local Terminal Equipment supplies a free-running 4.096MHz clock to the Receive Serial
Clock input. The Receive High-speed Back-plane Interface of the framer then sends out serial data at every
other rising edge of the Receive Serial Clock. The local Terminal Equipment samples the serial data at every
other falling edge of the clock.
The Terminal Equipment take in data grouped in 256-bit frame 8000 times every second. Each frame consists
of thirty-two octets as in E1. The Receive High-speed Back-plane Interface maps a 193-bit T1 frame into this
256-bit format as described below:
1.
The F-bit is mapped into MSB of the first E1 Time-slot. The framer will insert seven "don't care" bits to the
rest of the first octet that would be ignored by the local Terminal Equipment.
2.
Payload data of T1 Time-slot 0, 1 and 2 are mapped into E1 Time-slot 1, 2 and 3.
3.
The Receive High-speed Back-plane Interface will stuff E1 Time-slot 4 with eight "don't care" bits that
would be ignored by the local Terminal Equipment.
4.
Following the same rules of Step 2 and 3, the Receive High-speed Back-plane Interface maps every three
time-slots of T1 payload data into four E1 time-slots.
The mapping of T1 frame into E1 framing format is shown in the table below.
The Receive Single-frame Synchronization input signal (RxSync_n) should pulse HIGH at the beginning of the
256-bit frame indicating start of the frame. By sampling the HIGH pulse of the Receive Single-frame
Synchronization signal, the framer can identity the beginning of a DS1 frame and start pumping payload data
out.
T
ABLE
46: T
HE
MAPPING
OF
T1
FRAME
INTO
E1
FRAMING
FORMAT
T1
F-Bit
TS0
TS1
TS2
Don't Care Bits
TS3
TS4
TS5
E1
TS0
TS1
TS2
TS3
TS4
TS5
TS6
TS7
T1
Don't Care Bits
TS6
TS7
TS8
Don't Care Bits
TS9
TS10
TS11
E1
TS8
TS9
TS10
TS11
TS12
TS13
TS14
TS15
T1
Don't Care Bits
TS12
TS13
TS14
Don't Care Bits
TS15
TS16
TS17
E1
TS16
TS17
TS18
TS19
TS20
TS21
TS22
TS23
T1
Don't Care Bits
TS18
TS19
TS20
Don't Care Bits
TS21
TS22
TS23
E1
TS24
TS25
TS26
TS27
TS28
TS29
TS30
TS31