COM20020_00 Datasheet, PDF (44/82 Pages) SMSC Corporation – Universal Local Area Network Controller with 2K x 8 On-Board RAM

BIT
BIT NAME
3 Enhanced
Functions
2 No Synchronous
1,0 Reconfiguration
Timer 1, 0
SYMBOL
EF
NOSYNC
RCNTM1,0
DESCRIPTION
This bit is used to enable the new enhanced functions in the
COM20020. EF = 0: Disable (Default), EF = 1: Enable. If EF
= 0, the timing and function is the same as in the
COM20020, Revision B. See appendix “A”. EF bit must be
‘1’ if the data rate is over 5Mbps.
EF bit should be ‘1’ for new design customers.
EF bit should be ‘0’ for replacement customers.
This bit is used to enable the SYNC command during
initialization. NOSYNC= 0, Enable (Default) The line must
be idle for the RAM initialization sequence to be written.
NOSYNC= 1, Disable:) The line does not have to be idle for
the RAM initialization sequence to be written. See appendix
“A”.
These bits are used to program the reconfiguration timer as a
function of maximum node count. These bits set the time out
period of the reconfiguration timer as shown below. The
time out periods shown are for 5 Mbps.
RCNTM1 RCNTM0
Time Out
Max Node Count
Period
0
0
420 mS
Up to 255 nodes
0
1
105 mS
Up to 64 nodes
1
0
52.5 mS
Up to 32 nodes
1
1
26.25 mS*
Up to 16 nodes
Note*: The node ID value 255 must exist in the network for
26.25 mS timeout to be valid.
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