CN8478 Datasheet, PDF (99/221 Pages) Conexant Systems, Inc – Multichannel Synchronous Communications Controller (MUSYCC)

CN8478/CN8474A/CN8472A/CN8471A
Multichannel Synchronous Communications Controller (MUSYCC™)
5.0 Memory Organization
5.2 Descriptors
5.2.2.2 Service Request
The Service Request is a register per channel group within the host interface
containing a bit field where instructions are written to MUSYCC by the host. The
following instructions are supported:
• Perform device reset and initialization
• Perform channel group reset and initialization
• Configure a channel
• Read specific descriptors from within a Channel Group Descriptor
• Activate a channel
• Deactivate a channel
• Jump (re)activate a channel
• No-operation command
A service request is issued to a specific channel group within MUSYCC. The
channel group then acknowledges by sending a service request acknowledge
interrupt descriptor back to the host.
The soft-chip reset service request is the only service request not
acknowledged by MUSYCC.
Issuing multiple service requests to the same channel group successively
without first receiving acknowledgments from each request may cause the host to
lose track of which service request has been acknowledged, because MUSYCC
cannot uniquely acknowledge service requests for the same channel group. In
addition, issuing multiple simultaneous requests to the same channel group
causes indeterminate results within the channel group. To prevent these problems,
the host software must wait for a Service Request Acknowledgement (SACK)
after issuing any service request except for the soft chip reset request. The soft
chip reset request does not issue an acknowledgement, but this request is
guaranteed to be executed within two line clock periods.
Issuing a single service request to each supported channel group
simultaneously is supported, because MUSYCC acknowledges each one uniquely
with the Group ID bit field. Table 5-9 lists the bit fields and their descriptions of
the service request descriptor.
100660E
Conexant
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