6.0 Basic Operation
CN8478/CN8474A/CN8472A/CN8471A
6.4 Protocol Support
Multichannel Synchronous Communications Controller (MUSYCC™)
Long Message (LNG)
In the case of a Long Message (LNG) error, the received HDLC message size is
determined to be greater than the maximum allowed message size (per MAXSEL
in Channel Configuration Descriptor).
Reason:
•
Incorrect transmission of HDLC messages from the distant end.
Effects:
•
•
•
The Interrupt Descriptor in Interrupt Queue is ERROR = LNG, DIR = 0
(if MSKMSG = 0 in Receive Channel Configuration Descriptor).
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 = LNG (if INHRBSD = 0 in Receive 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.
•
Short Message (SHT)
In the case of a Short Message (SHT), the total received HDLC message size
(including FCS) is less than the number of FCS bits specified for the receive
channel. In other words, for a channel configured for 16-bit FCS, a minimum of
an 8-bit payload must be received to avoid a short message error. For this
example, three octets must be received—one octet for payload and two for FCS.
Receiving two octets would be considered a short message.
Reasons:
•
•
Bit errors during transmission.
Incorrect transmission of HDLC messages from the distant end.
Effects:
•
The Interrupt Descriptor in Interrupt Queue is ERROR = SHT, DIR = 0 (if
MSKIDLE = 0 in Receive Channel Configuration Descriptor).
Maintains ownership of current Message Descriptor.
The BLP resumes scanning for opening flag of the next HDLC message.
Simultaneously, MUSYCC checks for Message Descriptor ownership
before proceeding with bit-level operations.
•
•
•
Channel Level Recovery Actions:
None required.
•
6-42
Conexant
100660E
CONEXANT [ CONEXANT SYSTEMS, INC ]
