
XRT84L38
316
OCTAL T1/E1/J1 FRAMER
REV. 1.0.1
9.0
DS1 TRANSMIT FRAMER BLOCK
9.1
How to Configure XRT84L38 to Operate in DS1 Mode
The XRT84L38 Octal T1/E1/J1 Framer supports DS1, J1 or E1 framing modes. Since J1 standard is very
similar to DS1 standard with a few minor changes, the J1 framing mode is included as a sub-set of the DS1
framing mode. All eight framers within the XRT84L38 silicon can be individually configured to support DS1, J1
or E1 framing modes.
N
OTE
:
If transmitting section of one framer is configured to support either one of the framing modes, the receiving section
is automatically configured to support the same framing modes.
The T1/E1 Select bit of the Clock Select Register (CSR) controls which framing mode, that is, T1/J1 or E1,
supported by the framer. The table below illustrates configurations of the T1/E1 Select bit of the Clock Select
Register (CSR).
CLOCK SELECT REGISTER (CSR) (INDIRECT ADDRESS = 0XN0H, 0X00H)
Since J1 and DS1 are two very similar standards, to configure the framer to run in J1 mode, the user has to
select DS1 mode by setting the T1/E1 Select bit of the Clock Select Register to 1 first.
The next step is to set the J1 CRC Calculation bit of the Framing Select Register (FSR). If this bit is set to 1,
the XRT84L38 will do CRC-6 calculation in J1 mode. That is, the CRC-6 calculation is based on the actual
values of all 4,632 bits in DS1 multi-frame including framing bits. If this bit is set to 0, the XRT84L38 will
perform CRC-6 calculation in DS1 mode. That is, the CRC-6 calculation is done based on the actual values of
4,608 payload bits of a DS1 multi-frame and assumes that all the framing bits are one.
The table below shows configurations of the J1 CRC Calculation bit of the Framing Select Register (FSR).
FRAMING SELECT REGISTER (FSR) (INDIRECT ADDRESS = 0XN0H, 0X07H)
The table below provides summary of how to select different operating modes for the XRT84L38 framer.
The purpose of the DS1 Transmit Framer block is to embed and encode user payload data into frames and to
route this DS1 frame data to the Transmit DS1 LIU Interface block. Please note that the XRT84L38 has eight
(8) individual DS1 Transmit Framer blocks. Hence, the following description applies to all eight of these
individual Transmit DS1 Framer blocks.
B
IT
N
UMBER
B
IT
N
AME
B
IT
T
YPE
B
IT
D
ESCRIPTION
6
T1/E1 Select
R/W
0 - The XRT84L38 framer is running in E1 mode.
1 - The XRT84L38 framer is running in T1 mode.
B
IT
N
UMBER
B
IT
N
AME
B
IT
T
YPE
B
IT
D
ESCRIPTION
5
J1 CRC
Calculation
R/W
In J1 format, CRC-6 calculation is done based on the actual values of all
payload bits as well as the framing bits.
In DS1 format, CRC-6 calculation is done based on the payload bits only
while assuming all the framing bits are one.
0 - The framer performs CRC-6 calculation in DS1 format.
1 - The framer performs CRC-6 calculation in J1 format. This feature per-
mits the driver to comply with J1 standard.
T1/E1 S
ELECT
BIT
OF
CSR
J1 CRC C
ALCULATION
BIT
OF
FSR
T1
Set to 1
Set to 0
J1
Set to 1
Set to 1
E1
Set to 0
-