CX28344 Conexant, CX28344 Datasheet - Page 59

• Manufacturer Part Number: CX28344
• Description: (CX2834x) Dual / Triple / Quad / Hex / Octal - Enhanced DS3 / E3 Framer
• Manufacturer: Conexant

CX28342/3/4/6/8 Data Sheet
28348-DSH-001-B
Table 2-2. Overhead Options
When the Frame Overhead bits are not chosen to be inserted via the data stream, the
following source options are provided: internally generated, taken from register, or
entered through an external pin. For enabling sourcing options, the Frame Overhead
bits are divided into groups where each group of overheads has its own sourcing
options. Some groups and their source options are different for C-bit parity and M13/
M23 mode of operation. The difference is in the C-bits, which are divided to more
groups in C-bit parity mode.
C-Bit Parity and M13/M23 Modes of Operation
The following groups of overheads have the same options for both operational modes.
!
!
!
The C-bits in M13/M23 modes are used as Justification Control bits and are all
supplied from the same source. Their options are as follows:
!
!
5.
Framing bits (F-bits and M-bits)—When the External-Data method is disabled, the
three M-bits and the 28 F-bits can be either generated internally by the framer
(when ExtFrmAl bit is 0) or inserted through TEXT pin (when ExtFrmAl bit is 1).
X-bits (RAI)—Can be either inserted through the TEXT pin (controlled by bit
ExtRAI in the Transmit Overhead Insertion 2 register) or can be generated by an
internal register setting (controlled by TxAlm[1:0] bits). When TxAlm[1:0] is set
to 01, bits X1 and X2 contain 0s regardless of other X-bits sourcing settings.
P-bits (parity bits)—Can be either internally calculated or inserted from TEXT pin
(controlled by bit ExtP in the Transmit Overhead Insertion 2 register). When set to
be calculated internally, the transmitter calculates the parity over 4704 payload
bits of each M-frame (even parity calculation is used) and inserts the result into
both P1 and P2 bits of the following M-frame.
Either to be inserted with the data stream (with or without the rest of the Overhead
bits) by setting ExtDat bit to 1 or ExtFEBE/Cj-bit to 0.
To be inserted through the TEXT external pin. This option is chosen by setting
ExtDat bit to 0 and ExtFEBE/Cj-bit to 1.
None of the Overhead bits are inserted with data (justification control and Stuff
Opportunity bits enter through external pin and other overload bits are internally
generated) by setting ExtDat to 0 and ExtFEBE/Cj-bit to 1 and ExtStf to 1.
Option
1
2
3
4
5
Mindspeed Technologies™
ExtDat
1
0
0
0
0
Setting of External Data
ExtFEBE/Cj
0
0
1
0
1
ExtStf
Functional Description
0
1
0
0
1
2
-
13