2.0 Functional Description
CN8223
2.3 Overhead Generation
ATM Transmitter/Receiver with UTOPIA Interface
2.3.2 Internal G.832 E3/E4 Modes
All framing overhead is generated automatically and the BIP octet is calculated
and inserted in the EM position. The BIP field can be errored using the
TXFEAC_ERRPAT register [0x03] and BIP Error Insert [bits 12–10 of
CONFIG_2 [0x01]. All undefined overhead octets are inserted externally as
described in Section 2.3.5, and individual overhead octets can be disabled (set to
all 0s) using Overhead Control [bits 3–0] of CONFIG_2 [0x01]. Internally
generated octets are FA1, FA2, EM, and MA. Overhead generation of G.832 E3
and E4 values is summarized in Table 2-9.
Table 2-9. G.832 E3 and E4 Overhead Values
Overhead Bits
FA1/FA2
CN8223 Operation
Inserts standard values (0xF6, 0x28) or can be inserted externally through port TXOVH[7:0]. If this
bit is disabled, the value is 0x00.
EM
Calculates and inserts BIP8. Errors can be inserted using the TXFEAC_ERRPAT register. Allows
single error insertion or all 0 value (continuous error).
TR
Always inserted through port TXOVH[7:0].
MA
Calculates and inserts line FEBE based on incoming EM errors. Can be set for FEBE = all 1s or all 0s.
Inserts FERF and timing marker from register. Can be disabled to all-0s or inserted from
TXOVH[7:0].
NR
GC
P1
P2
Always inserted through port TXOVH[7:0].
Inserted externally through port TXOVH[7:0] or from internal HDLC formatter, if enabled.
E4 mode only. Always inserted through port TXOVH[7:0].
E4 mode only. Always inserted through port TXOVH[7:0].
2.3.3 Internal G.751 E3 Mode
The FAS pattern is automatically generated by the transmitter circuitry. The
transmitter also inserts the A bit as determined from Transmit Alarm Control
[bit 6] of CONFIG_2 [0x01]. Overhead generation of G.751 E3 values is
summarized in Table 2-10.
Table 2-10. G.751 E3 Overhead Values
Overhead Bits
CN8223 Operation
FAS
10-bit pattern internally generated—1111010000. No error
insertion.
A
N
Alarm bit set from CONFIG_2, bit 6.
Data or all 1s from internal HDLC formatter when enabled.
2-14
Conexant
100046C
CONEXANT [ CONEXANT SYSTEMS, INC ]
