CN8478 Datasheet, PDF (78/221 Pages) Conexant Systems, Inc – Multichannel Synchronous Communications Controller (MUSYCC)

4.0 Serial Interface
4.5 Channelized Port Mode
CN8478/CN8474A/CN8472A/CN8471A
Multichannel Synchronous Communications Controller (MUSYCC™)
4.5.4 Change-of-Frame Alignment
A Change of Frame Alignment (COFA) condition is defined as a frame
synchronization event detected when it is not expected, and includes the detection
of the first occurrence of frame synchronization when none is present.
When the serial interface detects a COFA condition, an internal COFA signal
is asserted for one frame period. During that period, MUSYCC’s channel group
processor terminates all active messages during the channel map processing.
For each receiver channel found to be active and processing a message during
the RCOFA event, each of these channels’ Buffer Status Descriptor is written
with the COFA error encoding. The Buffer Status Descriptor is written if
configured to do so in the Group Configuration Descriptor. MUSYCC then
proceeds to the next Message Descriptor in the list of messages.
When the internal COFA is deasserted, MUSYCC generates an Interrupt
Descriptor with the COFA error encoding if the interrupt is not masked in the
Group Configuration Descriptor. If a synchronization signal is received
(low-to-high transition on TSYNC or RSYNC) while the internal COFA is
asserted, an Interrupt Descriptor with the COFA interrupt encoding is generated
immediately if this interrupt is not masked. COFA detection is not applicable to
the N x 64 serial port mode.
4.5.5 Out-of-Frame
The Receiver Out-of-Frame (ROOF) signal is asserted by the physical T1 or E1
interface sourcing the channelized data to MUSYCC. This signal indicates the
interface device has lost frame synchronization.
In the case of multiplexed E1 lines (2xE1 or 4xE1), the ROOF input signal on
a given port can be asserted and deasserted as time slots are received from an
out-of-frame E1 followed by an in-frame E1.
The state of ROOF is evaluated on a bit-by-bit basis when processing data
from a time slot. When ROOF assertion is detected by the receiver serial
interface, MUSYCC checks the OOFABT bit in the Group Configuration
Descriptor. If the OOFABT bit is set (i.e., 1), MUSYCC terminates any active
messages for all mapped and active channels in the channel group. If the
OOFABT bit is not set (i.e., 0), MUSYCC continues to process the received data
but still asserts the OOF Interrupt Descriptor unless it is masked.
For each receive message terminated during the OOF condition, the
corresponding Message Descriptor’s owner bit is returned to the host, and a
Buffer Status Descriptor is written with the OOF error encoding. The Buffer
Status Descriptor is written to host memory only if configured to do so on a per
group basis in the Group Configuration Descriptor.
MUSYCC then proceeds to the next Message Descriptor in the list of messages.
Two frame synchronization events (via external sync or flywheel sync) after ROOF is
asserted, MUSYCC generates an interrupt descriptor with the OOF error encoding if
the interrupt is not masked in the Group Configuration Descriptor.
As ROOF is deasserted, MUSYCC immediately restarts normal bit level
processing on all mapped and active channels. Two frame synchronization events
after deassertion of ROOF is detected, MUSYCC generates an interrupt
descriptor with the Frame Recovery (FREC) interrupt encoding if the interrupt is
not masked (as indicated in Table 5-10, Group Configuration Descriptor).
4-8
Conexant
100660E