CX28344 Conexant, CX28344 Datasheet - Page 61

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

CX28342/3/4/6/8 Data Sheet
2.1.1.2
28348-DSH-001-B
E3–G.751 Mode
E3-G.751 frame structure has 24 frame Overhead bits, which are divided as follows:
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The External-Data source option for the E3-G.751 mode provides the following
options of framing bits insertion with the data stream:
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When the frame Overhead bits are not chosen to be inserted via the data stream, the
following source options are provided for each group of frame Overhead bits:
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10 frame alignment signal (FAS) bits
Alarm indication to the remote digital multiplex equipment (A-bit) bit
Bit reserved for national use (N-bit)
12 justification service bits (Cj-bits)
All Overhead bits can be inserted with the data stream by setting bit ExtDat to 1.
Only Cj-bits enter with the data stream and the 4 Stuff Opportunity bits are
inserted via TEXT by setting bit ExtDat to 0 and bit ExtFEBE/Cj to 0 and ExtStf =
0. The rest of the Overhead bits (FAS, A, and N) source is set separately.
Both Cj-bits and the 4 Stuff Opportunity bits are inserted with the data by setting
ExtDat=0 and ExtFEBE/Cj = 0 and ExtStf = 0.
None of the Overhead bits or stuff bits are inserted with data (they are either
generated internally or enter through external pin) by setting bits ExtDat and
ExtFEBE/Cj to 0, 1 respectively and ExtStf = 1.
FAS—Bits 1 to 10 of set 1 are used as the frame alignment signal. Those bits are
generated automatically internally by the transmitter circuit and inserted at the
beginning of each E3-G.751 frame transmission. The 10 FAS bits have the
sequence: 1111010000 (transmitted from left to right), or they can be inserted
through the TEXT pin by setting of bit ExtFrmA1.
A-bit—Bit 11 of set 1 is the alarm indication to the remote digital multiplex
equipment bit (used to send RAI alarm signal). This bit can be automatically
internally generated, controlled by a register or inserted through the TEXT pin.
Automatic RAI generation is enabled by setting bit AutoRAI in the Transmit
Overhead Insertion 1 Control register to 1. In this mode as long as a Loss of Signal
(LOS) condition or loss of frame alignment—Out of Frame (OOF) are detected at
the RCV, the TRN automatically inserts 1 at the transmitted A-bit. When LOS and
OOF conditions are not detected, the TRN sets the transmitted A-bit to 0 (no RAI
alarm). When AutoRAI = 0, setting ExtRAI bit at the Transmit Overhead Insertion
2 Control register to 1 causes A-bit insertion through TEXT pin. For as long as
TxAlm [1] is set to 1, the A-bit contains 1 regardless of other A-bits sourcing
settings.
N-bit—Bit 12 of set 1 is reserved for national use. Its value can be taken from the
TEXT input pin when bits DLMod [2] and DLMod [1] in the Transmit Overhead
Insertion 1 Control register are both set to 1. It can be automatically set to 1 by the
framer when bit DLMod [2] is set to 0, or it can be chosen internally generated by
registers when DLMod [2] and DLMod [1] are set to 10. The last option
implements a LAPD data link with HDLC formatting over the N-bit using an
internal FIFO buffer. For more details about using the data link FIFO buffer, see
Section
Cj-bits—The justification bits are provided either to the transmitter framer with
the data stream, or by the TEXT external overhead input pin (when ExtFEBE/Cj is
set to 1) when the option of providing them with the data stream is disabled.
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Mindspeed Technologies™
Functional Description
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