CN8478 Datasheet, PDF (165/221 Pages) Conexant Systems, Inc – Multichannel Synchronous Communications Controller (MUSYCC)

CN8478/CN8474A/CN8472A/CN8471A
Multichannel Synchronous Communications Controller (MUSYCC™)
6.0 Basic Operation
6.4 Protocol Support
Table 6-13. Message Configuration Descriptor (2 of 2)
Bit
Field
Name
Value
24
PADEN
0
1
23:16
PADCNT[7:0]
0
15
REPEAT
0
1
14:0
RSVD
0
Description
Pad Fill Disabled. One shared opening/closing flag
(7Eh) is inserted before sending next message
Pad Fill Enabled. Also, see PADCNT bit field.
Pad Count. When PADEN = 1, PADCNT indicates the
minimum number of idle codes to be inserted
between the closing flags and the next opening flag
(7Eh).
If PADCNT = 2 and IC = 1, for example, yields the
bit pattern 7Eh..FFh..FFh..7Eh
There is no indication by MUSYCC if more than
PADCNT number of idle codes are inserted.
Repeat Message Transmission Disabled.
Repeat Message Transmission Enabled.
Reserved.
6.4.7 Bit-Level Operation
Each channel group provides two separate Bit-Level Processors (BLP) to service
the transmit and receive directions separately. Also, each channel group provides
two separate Direct Memory Access Controllers (DMAC) to service the transmit
and receive directions separately. The BLP and DMAC work in conjunction to
transfer serial data between the serial interface and shared memory. BLPs
perform the required bit-level processing based on the protocol mode assigned to
the channel and direction.
DMACs access the data to transmit or store the received data to shared
memory (via the host interface). Each DMAC seeks out the next Message
Descriptor to service for each active channel and direction. This information is
available from the Channel Group Descriptor in shared memory which has
information locating the message list for each channel direction. A Buffer
Descriptor within each Message Descriptor along with the protocol mode set for
the channel-direction drives the treatment of the receive and transmit bit stream.
Bit-level operations vary between HDLC and transparent modes. The
differences relate to protocol-specific support, as well as to the treatment of the
bit stream during abnormal conditions. Additionally, bit-level operations are
independent and sometimes differ between the transmitter and the receiver.
100660E
Conexant
6-31