cx28250 Mindspeed Technologies, cx28250 Datasheet - Page 49

• Manufacturer Part Number: cx28250
• Description: Cx28250 Atm Physical Interface Phy Devices
• Manufacturer: Mindspeed Technologies

CX28250
ATM Physical Interface (PHY) Devices
2.3.1 Loss of Signal
2.3.2 Section Overhead
28250-DSH-002-C
2.3.2.2 Loss of Frame
2.3.2.1 A1, A2
By default, the scrambled STS-3c/STM-1 data is monitored for the absence of 1s.
When 1620 consecutive octets (6 SONET rows) of 0s are detected, LOS is
declared. LOS is cleared when two valid framing words (A1/A2) are received
with no intervening LOS detection. The LOS condition is reflected in register
RXSEC (0x45) bit 5. In addition, StatOut[7] is asserted if Status Output Pin
Mode, bit 2 of the GEN register (0x00), is enabled.
transitions on the incoming data. Thus either the all zeroes or a “stuck at 1”
condition will result in the device declaring LOS. This only applies to the
CX28250-26 version.
NOTE:
The Section Overhead handles the transport of the STS-3c/STM-1 frame across
the physical medium and section-level communications. Its functions are framing
and scrambling on the transmit side, and section error monitoring on the receive
side. The transmit and receive functions of the Section Overhead bytes are
described in
Table 2-3. Section Overhead Transmit and Receive Functions
The STS-3c/STM-1 framing bytes, A1 and A2, are used to determine OOF status.
When these octets match the framing pattern, the status is “in-frame.” When there
are four consecutive frames with one or more framing pattern errors, OOF is
declared. This condition asserts StatOut[6] and is reflected in register RXSEC
(0x45) bit 4. The transmit A1/A2 bytes can be disabled by writing bit 4 in the
TXSEC (0x0C) register to 1. A1 can be inverted by writing bit 7 in the ERRINS
(0x06) register to 1. One valid A1/A2 frame clears OOF status.
A Loss of Frame (LOF) condition is declared when Out-of-Frame (OOF) status
exists for 24 consecutive frames. This condition is cleared when OOF status has
been clear for 8 consecutive frames. LOF is reflected in register RXSEC (0x45)
bit 3.
A1/A2
B1
D1, D2, D3
J0
Z0
1
The CX28250-26 version can also be configured to detect the lack of
, Z0
Byte
If the LSigDet pin goes low, then the receive data is internally forced to all
zeros to ensure that LOS is recognized.
2
Mindspeed Technologies
Table
F6/28 hex or disable 00
Calculated, error insertion
option
00 hex or external serial
access
01 hex or 64-byte trace buffer
Controlled by the TXZ01 and
TXZ02 registers (defaults to
02 and 03 respectively)
2-3.
Transmit
2.3 SONET/SDH Framer and Overhead Processor
™
Monitor out of frame state machine
Checked, errors counted
External serial access
Monitor Rx trace buffer, interrupt on
change
Stored in the RXZ01 and RXZ02
registers (interrupt generated on
change)
2.0 Functional Description
Receive
2-13