CN8478/CN8474A/CN8472A/CN8471A
6.0 Basic Operation
Multichannel Synchronous Communications Controller (MUSYCC™)
6.3 Channel Operation
5. At end of message, Interrupt Descriptors and Buffer Status Descriptors can
be written out to shared memory (see 3)—depending on the masking of
interrupts and allowance of Buffer Descriptor overwrites.
6. Read Next Message Descriptor.
7. Go to 3.
NOTE: MUSYCC responds to either a JUMP or ACTIVATE service request by
reading first the head pointer and then the Message Descriptor pointed to
by the Head Pointer. Therefore, software must set up the new head pointer
and Message Descriptors (i.e., buffer list) before issuing either a JUMP or
ACTIVATE service request.
6.3.17 Channel Deactivation
After the channel has been activated, channel deactivation via a service request
suspends activity on an individual channel-direction by stopping that channel’s
processing of the current buffer list. The only indication that MUSYCC has
completely stopped its list processing is a SACK interrupt. Therefore, the host
must wait for a SACK before setting up the new buffer list.
Each channel within a channel group consists of a transmitter and receiver
section. Each section is independent of the other and maintains its own state
machine and configuration registers. To deactivate both transmitter and receiver
sections, two separate service requests are required—one directed to the
transmitter and one to the receiver. MUSYCC responds to each service request
with the SACK Interrupt Descriptor, which notifies the host that the task was
completed.
A channel deactivation is an asynchronous command from the host interface
to a transmit or receive section of a channel to suspend bit-level processing and
halt memory transfers into shared memory.
6.3.17.1 Transmit
Channel Deactivation
The following describes what MUSYCC does when the transmit 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 outbound bits to the serial
port is immediately and asynchronously disabled. The data output pin,
TDAT, is three-stated or held at logic 1, depending on the bit field TRITX
in the Port Configuration Descriptor. Data transfers from 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.
6.3.17.2 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.
100660E
Conexant
6-23
CONEXANT [ CONEXANT SYSTEMS, INC ]
