2.0 Functional Description
CN8223
2.3 Overhead Generation
ATM Transmitter/Receiver with UTOPIA Interface
2.3.6 Receive Framing Overhead Interface
An octet interface is available for external observation of all framing overhead in
STS-1/STS-3c/STM-1 and G.832 E3/E4 framing modes. The interface consists of
two output clocks on ROVH_CLK[1,0], two output markers on RMRKR[1,0],
and an 8-bit output bus RXOVH[7:0]. Timing for this interface is illustrated in
Figure 2-13. There is a clock pulse on the ROVH_CLK[1] output for each section
and line overhead octet in STS-1 and STS-3c/STM-1 modes and for all overhead
octets in G.832 E3 and E4 modes. There is a clock pulse on the ROVH_CLK[0]
output for each path overhead octet in STS-1 and STS-3c/STM-1 modes.
The RMRKR[1,0] outputs and the bus output are set up prior to the rising
edge of the clocks and can be sampled externally on the rising edge of
ROVH_CLK[1,0]. The RMRKR[1] output is high during row 1 overhead in all
modes (A1, A2, and C1 in STS-1/STS-3c/STM-1 modes and FA1, FA2 in G.832
E3/E4 modes). The RMRKR[0] output is high during row 1 path overhead (octet
J1) in STS-1 and STS-3c/STM-1 modes. There are two marker and clock outputs
for STS-1 and STS-3c/STM-1 modes because the SONET frame and payload
envelopes can be offset from each other.
Mode
Overhead Octets Output per Frame
36
90
7
STS-1
STS-3c/STM-1
G.832 E3
G.832 E4
16
In STS-1/STS-3c/STM-1 modes, the contents of octets D1, D2, and D3 are
provided to the internal HDLC receiver. The GC octets of the E3 and E4 formats
are also provided to the HDLC receiver. Terminal data link bits in DS3 mode (C
bits of subframe 5) and the N-bit in G.751 E3 mode are also provided to the
HDLC receiver.
Figure 2-13. Receive Framing Overhead Interface Timing
ROVH_CLK[1]
RMRKR[1]
ROVH_CLK[0]
RMRKR[0]
RXOVH[7:0]
A1 A2 C1
2-18
Conexant
100046C
CONEXANT [ CONEXANT SYSTEMS, INC ]
