COM20020D Datasheet, PDF (33/72 Pages) SMSC Corporation – ULANC Revision D Universal Local Area Network Controller with 2K x 8 On-Board RAM

4,3 Extended
Timeout 1,2
2 Backplane
1,0 Sub Address 1,0
Table 10 - Configuration Register
ET1, ET2
These bits allow the network to operate over longer distances
than the default maximum 2 miles by controlling the
Response, Idle, and Reconfiguration Times. All nodes should
be configured with the same timeout values for proper
network operation. For the COM20020D with a 20 MHz
crystal oscillator, the bit combinations follow:
BACK-
PLANE
SUBAD
1,0
Reconfig
Response Idle Time Time
ET2
ET1 _{Time (µS) (µS)}
(mS)
0
0
596.6
656
840
0
1
298.4
328
840
1
0
149.2
164
840
1
1
37.4
41
420
Note: These values are for 5Mbps and RCNTMR[1,0]=00.
Reconfiguration time is changed by the RCNTMR1 and
RCNTMR0 bits.
A logic "1" on this bit puts the device into Backplane Mode
signaling which is used for Open Drain and Differential Driver
interfaces.
These bits determine which register at address 07 may be
accessed. The combinations are as follows:
SUBAD1
0
0
1
1
SUBAD0 Register
0 Tentative ID
1 Node ID
0 Setup 1
1 Next ID
See also the Sub Address Register.
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