TMC2074-NE SMSC, TMC2074-NE Datasheet - Page 36

• Manufacturer Part Number: TMC2074-NE
• Description: Network Controller & Processor ICs Standalone Mode CircLink Cntlr
• Manufacturer: SMSC

Specifications of TMC2074-NE

• Product: Controller Area Network (CAN)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

2.7.2
Revision 0.2 (10-23-08)
Standalone mode
In Standalone mode, CircLink independently executes send and receive sequences without a CPU. Refer
to section 2.10 - Standalone Mode for more details.
Communication Mode
Free format mode
Free format mode is retained from the original ARCNET specification. This mode is optimal for transferring
large amounts of data at once. CPU controls a series of sequence such as "Packet preparation → Issuing
TX command → Interruption handling after the end of TX" at sender and "Receive command issuing →
Interrupt handling after the end of RX→ Packet read" at receiver.
Since CircLink initiates the actual TX upon receipt of a token addressed to the node, the time between a
TX command being issued and TX starting varies depending on the line status. The free format mode is a
"packet-oriented" transfer mode that assumes a completion of packet preparation before issuing a TX
CMD, so its real-time performance is not as high as that of the remote buffer mode “token-oriented” mode.
On the other hand, the free format mode has no limitation on the packet data structure, and it can handle
free format packets. Moreover, communications in this mode are initiated only by writing a TX CMD,
thereby reducing traffic on the network.
Remote buffer mode
Remote Buffer mode, a CircLink enhancement, optimizes real-time performance. In this mode CircLink can
be handled as a simple data buffer like "write data into the CircLink at any time" at a transmit node and
"read data from the CircLink at any time" at a receiver node “.
Since the remote buffer mode is a "token-oriented" mode that features automatic transmission each time a
node receives a token (= sending right), preparation of the packet header portion (SID, DID, and CP) is
Figure 8 - Packet Structure of Free Format Mode (Example of 32 bytes/page)
RAM-ADRS
8 bit constitution
(W16=L,WDMD=0)
1E
00
01
02
03
04
05
1F
.
.
.
.
7
Format
Free
DID
SID
CP
DATASHEET
0
RAM-ADRS
16 bit constitution
Page 36
(W16=L,WDMD=1 OR W16=H)
1E
00
02
04
.
.
.
.
15
dummy
DID
1
Format
Free
8 7
Dual Mode CircLink™ Controller
SID
CP
0
0
SMSC TMC2074
Datasheet