CN8478 Datasheet, PDF (174/221 Pages) Conexant Systems, Inc – Multichannel Synchronous Communications Controller (MUSYCC)

6.0 Basic Operation
6.4 Protocol Support
CN8478/CN8474A/CN8472A/CN8471A
Multichannel Synchronous Communications Controller (MUSYCC™)
Out of Frame (OOF)
Frame Check
Sequence (FCS) Error
Out-of-frame or loss-of-frame indicates that the entire serial data stream is invalid
and data cannot be recovered from such a signal. In this case, out-of-frame of the
incoming signal occurred while in the midst of receiving an HDLC message and
copying the data to shared memory.
Reason:
• MUSYCC writes the 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:
• MUSYCC writes the Interrupt Descriptor in Interrupt Queue with
ERROR = OOF, DIR = 0 (if MSKOOF = 0 in Group Configuration
Descriptor).
• If bit field OOFABT = 0, BLP, and DMAC continue as if no errors
occurred and transfer received data into shared memory buffers normally.
• If bit field OOFABT = 1 and is currently receiving an HDLC message, the
received data in the internal FIFO buffer is discarded and lost to the host.
DMAC accesses the Next Message Pointer from the current Message
Descriptor. MUSYCC returns ownership of the current Message
Descriptor by writing the Receive Buffer Status Descriptor with
ONR = HOST, ERROR = OOF (if INHRBSD = 0 in Receive Channel
Configuration Descriptor).
• Regardless, the BLP continues scanning for opening flag.
• Simultaneously, DMAC checks for Message Descriptor ownership before
transferring received data to shared memory.
• Receive channel recovers automatically.
Channel Level Recovery Actions:
• None required.
In the case of an FCS error, the frame check sequence (or CRC) calculated for the
received HDLC message by MUSYCC does not match the FCS sent within the
HDLC message.
Reason:
• Bit errors during transmission.
Effects:
• The Interrupt Descriptor in Interrupt Queue with ERROR = FCS, DIR = 0
(if MSKMSG = 0 in Channel Configuration Descriptor).
• The entire HDLC message already copied to shared memory buffers.
• DMAC accesses the Next Message Pointer from the current Message
Descriptor.
• Returns ownership of the current Message Descriptor to the host by
writing the Receive Buffer Status Descriptor with ONR = HOST,
ERROR = FCS (if INHRBSD = 0 in Channel Configuration Descriptor).
• The BLP scans for the opening flag of the next HDLC message.
• Simultaneously, DMAC checks for Message Descriptor ownership before
transferring received data to shared memory.
Channel Level Recovery Actions:
• None required.
6-40
Conexant
100660E