28478-DSH-002-E_15 Datasheet, PDF (144/195 Pages) M/A-COM Technology Solutions, Inc. – Multichannel Synchronous Communications Controller

Basic Operation
6.3.17.2
Receive Channel Deactivation
The following describes what MUSYCC does when the receive channel is deactivated:
1. Current message processing is terminated destructively; that is, data can be lost and messages prematurely
aborted.
2. The bit-level processor responsible for handling inbound bits from the serial port is immediately and
asynchronously disabled. Data transfers to shared memory are halted.
3. The channel direction remains in the suspended state until the channel is activated. The current channel
direction configuration is maintained.
6.3.18
Channel Jump
A channel jump request is issued by the host via a service request. For a receiver, channel jumps are the same as
channel activation.
For a transmitter, channel jumps are non-destructive to currently serviced messages. The channel state is not reset
as in the channel activate sequence. Therefore, a transmitter channel must be activated first, then subsequent
jump requests can be made using the channel jump service request. For a transmitter, channel jumps provide a
non-destructive way to start transmitting a new message list. MUSYCC waits until the completion of the current
message before jumping to a message list pointed to by a new Head Pointer.
A jump request is issued by the host via a service request towards a channel in a channel group in MUSYCC.
NOTE:
The service request acknowledge (via the SACK Interrupt Descriptor) for the jump service
request—specifically for the transmit direction—will not be output towards the host until
after the current message is transmitted. For applications with long messages to transmit,
the jump service request must be used with care.
6.3.19
Frame Alignment
Each serial port frame consists of a fixed number of bits grouped into time slots according to the frame alignment
supplied by the serial port TSYNC and RSYNC signals. MUSYCC must be provided at least one external
synchronization pulse on the TSYNC and RSYNC input pins after the respective channel group is enabled. After
this initial sync pulse, MUSYCC tracks subsequent serial port frame boundaries using its internal flywheel
mechanism or the next applied sync pulse.
NOTE:
Nx64 serial port mode does not operate the internal flywheel and therefore requires
periodic TSYNC and RSYNC pulses to keep track of serial port frame boundaries.
In addition to tracking serial port frame boundaries, the internal flywheel generates a frame synchronization signal
that can be selected to control the channel group's alignment of Transparent mode channel data streams. By
default, the frame synchronization signal from the internal flywheel determines Transparent mode channel data
stream alignment. If external data stream synchronization is preferred, the SFALIGN bit field in the Group
Configuration Descriptor can be set to expect this synchronization signal to come from the serial port TSYNC and
RSYNC input pins. While SFALIGN is set, the internal flywheel continues to operate, but the synchronization signal
from the flywheel is not used to determine data stream alignment. Instead, alignment is provided by the external
framer device which is allowed to strobe the sync input pins at periodic frame intervals or at any desired multiple of
the frame interval (i.e., superframe).
Each serial port frame carries stream data from one or more packetized HDLC or unpacketized Transparent mode
channels. Although channels are mapped to specific time slots within the serial port frame, each channel's data
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