CN8478 Datasheet, PDF (170/221 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™)
6.4.8.3 Transmit Errors
Underflow Due to Host
Ownership of Buffer (ONR)
Underflow Due to Internal
FIFO Buffer Under-Run
(BUFF)
6-36
Effects:
• Interrupt Descriptor in Interrupt Queue with EVENT = SFILT, DIR = 0
(if MSKSFILT = 0 in Receive Channel Configuration Descriptor).
• BLP discards the received message in the FIFO.
• BLP and DMAC continue with normal message processing.
Transmit errors are service-affecting and require a corrective action by a
controlling device to resume normal bit-level processing.
In this case, MUSYCC attempts to access the [next] Message Descriptor when the
prior descriptor contained only a portion of the message (EOM = 0), and
MUSYCC finds that ownership of the [next] descriptor has not been granted by
the host (i.e., the next buffer is host-owned).
This error results when currently transmitting an HDLC message, and no
additional descriptors are available in a timely manner.
Once a descriptor is granted, however, MUSYCC assumes ownership of the
message buffer and continues reading data until the end of buffer is reached. If the
host reclaims the buffer without MUSYCC granting ownership back to the host, a
host error occurs, and the effects are indeterminate.
Reason:
• Degradation of the host subsystem or application software performance.
Effects:
• Partial HDLC message transmission has occurred.
• Interrupt Descriptor in Interrupt Queue with ERROR = ONR, DIR = 1
(if MSKBUFF = 0 in Transmit Channel Configuration Descriptor).
• Transmit channel enters abort state where the BLP transmits a repetitive
abort sequence of 16 consecutive 1s.
• Transmit Buffer Status Descriptor cannot be written.
• Message polling is automatically disabled.
• Transmit channel enters abort state.
Channel Level Recovery Actions:
• Transmit channel reactivation is required.
In the case of underflow due to internal FIFO buffer under-run, the internal FIFO
buffer becomes empty when MUSYCC transmits data bits (at the serial interface
clock rate), and MUSYCC has ownership of a message buffer in shared memory.
Reasons:
• Degradation of the host subsystem or application software performance.
• Congestion of the PCI bus.
Effects:
• Interrupt Descriptor in Interrupt Queue with ERROR = BUFF, DIR = 1
(if MSKBUFF = 0 in Transmit Channel Configuration Descriptor).
• Transmit channel enters abort state where the BLP transmits a repetitive
abort sequence of 16 consecutive 1s.
• Message polling is automatically disabled.
• Transmit Buffer Status Descriptor is not written.
Channel Level Recovery Actions:
• Transmit channel reactivation is required.
Conexant
100660E