COM20019I_0610 Datasheet, PDF (34/70 Pages) SMSC Corporation – Cost Competitive ARCNET (ANSI 878.1) Controller with 2K x 8 On-Chip RAM

RAM
Cost Competitive ARCNET (ANSI 878.1) Controller with 2K x 8 On-Chip
BIT
4,3
BIT NAME
Extended
Timeout 1,2
2
Backplane
1,0 Sub Address 1,0
SYMBOL
ET1, ET2
DESCRIPTION
These bits allow the network to operate over longer
distances than the default maximum 32 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 COM20019I 3V with a 20
MHz crystal oscillator, the bit combinations follow:
BACK-
PLANE
SUBAD
1,0
Response Idle Time Reconfig
ET2
ET1 Time (mS) (mS)
Time (S)
0
0
9.548
10.496 13.44
0
1
4.774
5.248
13.44
1
0
2.387
2.624
13.44
1
1
0.597
0.656
6.72
Note: These values are for 312.5 Kbps 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. This bit must be set to ‘1’ at the
COM20019I 3V.
These bits determine which register at address 07 may be
accessed. The combinations are as follows:
SUBAD1
SUBAD0
Register
0
0
Tentative I
0
1
Node ID
1
0
Setup 1
1
1
Next ID
See also the Sub Address Register.
BIT
BIT NAME
7
Pulse1 Mode
6
Four NACKS
5
Reserved
4
Receive All
Table 6.10 - Setup 1 Register
SYMBOL
P1MODE
FOUR
NACKS
RCVALL
DESCRIPTION
This bit determines the type of PULSE1 output driver used
in Backplane Mode. When high, a push/pull output is
used. When low, an open drain output is used. The
default is open drain.
This bit, when set, will cause the EXNACK bit in the
Diagnostic Status Register to set after four NACKs to Free
Buffer Enquiry are detected by the COM20019I 3V. This
bit, when reset, will set the EXNACK bit after 128 NACKs
to Free Buffer Enquiry. The default is 128.
Do not set. It must be 0.
This bit, when set, allows the COM20019I 3V to receive all
valid data packets on the network, regardless of their
destination ID. This mode can be used to implement a
network monitor with the transmitter on- or off-line. Note
that ACKs are only sent for packets received with a
destination ID equal to the COM20019I 3V's programmed
node ID. This feature can be used to put the COM20019I
3V in a 'listen-only' mode, where the transmitter is
disabled and the COM20019I 3V is not passing tokens.
Defaults low.
Rev. 10-31-06
Page 34
DATASHEET
SMSC COM20019I 3.3V Rev.C