CN8478 Datasheet, PDF (171/221 Pages) Conexant Systems, Inc – Multichannel Synchronous Communications Controller (MUSYCC)

CN8478/CN8474A/CN8472A/CN8471A
Multichannel Synchronous Communications Controller (MUSYCC™)
6.0 Basic Operation
6.4 Protocol Support
Change of Frame Alignment
(COFA) while Transmitting
HDLC Message
(T1/E1 modes)
6.4.8.4 Receive Errors
Overflow Due to Host
Ownership of Buffer while
Receiving HDLC Message
(ONR)
In the case of change of frame alignment while transmitting an HDLC message
(T1/E1 modes), the TSYNC input signal transitions from low to high when not
expected to do so by the frame synchronization flywheel mechanism. This error
only applies to ports configured for T1, E1, 2xE1 or 4xE1 signals. Frame
synchronization indicates the location of time slot 0 in the serial data stream.
Lacking frame synchronization, the transmitter cannot map and align time slots.
This error affects all active channels in the channel group.
Reason:
• T1/E1 signal failure is detected by the physical interface providing the
serial data, clock frequency, and synchronization to the serial interface on
MUSYCC.
Effects:
• Causes serial interface to enter COFA mode for one T1/E1 frame period
(125 µs)—not necessarily on a frame boundary.
• For every activated channel transmitting an HDLC message, the Transmit
channel enters an abort state where the BLP transmits a repetitive abort
sequence of 16 consecutive 1s.
• MUSYCC does not update the transmit Message Descriptor and does not
generate an EOB/EOM unless the message is already sent or the buffer is
already processed.
• MUSYCC stops polling any active transmit channels descriptor.
• After the COFA condition subsides, the channel is deactivated.
Channel Level Recovery Actions:
• Transmit channel reactivation is required.
Receive errors are service-affecting and require a corrective action by the host to
resume normal bit-level processing.
In the case of overflow due to host ownership of the buffer while receiving an
HDLC message, MUSYCC attempts to access the next Message Descriptor to
store a message or part of a message, and finds that ownership of the descriptor
has not been granted by the host.
This error results when currently receiving an HDLC message, and no
additional descriptors are available in a timely manner.
100660E
Conexant
6-37