CN8478 Datasheet, PDF (115/221 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
Table 5-18. Channel Configuration Descriptor (3 of 3)
Bit
Field
Name
Value
Description
3
MSKMSG
0
LNG, FCS, ALIGN, ABT Interrupt enabled. Receive only. When receiver detects
too-long message, FCS error, message alignment error, or abort condition, this
bit generates interrupt to indicate condition.
1
In order for MSKMSG=1 to disable all interrupts (LNG, FCS, ALIGN) the
MSKEOM must be set (i.e., 1).
2
MSKEOM
0
EOM Interrupt enabled. Receive and Transmit. Interrupt generated when end of
message detected.
1
EOM Interrupt disabled.
1
MSKBUFF
0
BUFF—Interrupts enabled. Receive and Transmit. Interrupt generated when
transmitter underflow buffer or receiver overflows buffer internally to MUSYCC.
ONR—Interrupts enabled. Receive and Transmit. Interrupt generated where
message pointer/descriptor is not available to MUSYCC where is expected.
(Refer to Figure 5-31, Interrupt Descriptor.)
1
BUFF—Interrupts disabled. ONR—Interrupts disabled.
0
RSVD
0
Reserved.
5.2.4 Message Level Descriptor
One message descriptor defines one data buffer where all or part of a message is
stored in shared memory. By linking message descriptors, numerous data buffers
are linked to support high-speed data links or large messages spread across a
number of smaller data buffers.
Depending on the transmission and reception rate of individual channels, the
numbers and sizes of message buffers can vary between channels and
applications. For high-speed lines, more and larger buffers can be used to provide
ample data storage while the host processes each message in the list of messages.
For low-speed lines, fewer and smaller buffers can be used as the host may be able
to process each message faster and the need to store messages is lessened.
Multiple smaller data buffers can be linked using message descriptors to store
one large message. In utilizing multiple buffers, the importance of keeping the
sequence of data buffers in order is obvious.
MUSYCC’s operation allows for the following:
• Multiple buffer lists
• Multiple and variable size buffers within a buffer list
• Multiple buffers storing a single message
• Sequencing of individual data buffers for a multi-buffer message
100660E
Conexant
5-29