TMC2074 datasheet(21/116 Pages) SMSC

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Dual Mode CircLink™ Controller

Datasheet

SMSC TMC2074

Page 21

Revision 0.1 (03-29-06)

DATASHEET

1.6.8

Page Size Selection

(PS[1:0]: Pin/Register)

Select page size per packet. The maximum number of nodes depends on the page size selection since the

packet buffer size is limited to 1 kByte. Page size can be selected by settings using register bits INIMODE

(bit 9); 0: selects pin, 1: selects register (The default is 0).

PS[1:0]

Page Size

Max Node Number

256 Byte

3 Node

128 Byte

7 Node

64 Byte

15 Node

32 Byte

31 Node

1.6.9

Maximum Node (MAXID) Number Setup

(MAXID[4:0]: Pin/Register)

The maximum node ID is set based on the number of nodes on the network. All nodes in each CircLink

network, therefore, should have the same maximum node ID. This minimizes the time required to

reconfigure the network. There are two methods to specify the maximum node ID, Either through pin or

nDIAG pin is set to L as the exception, however, the maximum node ID is automatically set to the largest

value. For more details, refer to section 2.11 - Diagnostic Mode.

1.6.10 Node ID Setup

(NID[4:0]: Pin/Register)

Set node ID. A unique number must be assigned to each node in the network with ascending order starting

from ID=01. ID = 00 and an ID larger than the maximum node ID are not valid. There are two methods to

assign the node ID, either through pin or register, settings depending on INIMODE (bit 7) 0: selects pin, 1:

select register (default is 0).

MAXID[4:0] determines the maximum node ID value. The token will be passed only around the nodes

whose IDs are equal to or less than the maximum ID value. . In the CircLink network, a node whose

MAXID[4:0] and NID[4:0] matches is the node initiating the token passing.. Even if this particular node is

absent from the network, the network reconfiguration time is greatly reduced because the network will be

only reconfigured by the nodes with IDs less than MAXID[4:0]. Since the maximum number of nodes is

fixed to MAXID[4:0] in a CircLink network, the original priority timer of ARCNET, (255 – ID) x 146

μs*,

which determines the time required for network reconfiguration, is modified to (MAXID[4:0]-ID) x 146

μs,

greatly reducing network reconfiguration time. Refer to section 2.4.2 - Reduction of Network

Reconfiguration Time for more details.

* 146

μs is defined under operation at 2.5 Mbps based on ARCNET protocol. That number is half at 5

Mbps.

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