com20020-5 Standard Microsystems Corp., com20020-5 Datasheet - Page 27

• Manufacturer Part Number: com20020-5
• Description: Com20020-5 Ulanc Universal Local Area Network Controller With 2k X 8 On-board Ram
• Manufacturer: Standard Microsystems Corp.

BIT
4,3
1,0
7
6
5
2
Reset
Command
Chaining Enable
Transmit Enable
Extended
Timeout 1,2
Backplane
Sub Address 1,0
BIT NAME
RESET
CCHEN
TXEN
ET1, ET2
BACK-
PLANE
SUBAD 1,0
TABLE 8 - CONFIGURATION REGISTER
SYMBOL
A software reset of the COM20020-5 is executed by writing a logic "1"
to this bit.
interface mode, nor does it affect the Configuration Register. The
only registers that the software reset affect are the Status Register,
the Interrupt Mask Register, and the Diagnostic Status Register. This
bit must be brought back to logic "0" to release the reset.
This bit, if high, enables the Command Chaining operation of the
device. Please refer to the Command Chaining section for further
details. A low level on this bit ensures software compatibility with
previous SMSC ARCNET devices.
When low, this bit disables transmissions by keeping nPULSE1,
nPULSE2 if in non-Backplane Mode, and nTXENABLE inactive.
When high, it enables the above signals to be activated during
transmissions. This bit defaults low upon reset. This bit is typically
enabled once the Node ID is determined, and never disabled during
normal operation. Please refer to the Improved Diagnostics section
for details on evaluating network activity.
These bits allow the network to operate over longer distances than the
default maximum 2 miles by controlling the Response, Idle, and
Reconfiguration Times.
same timeout values for proper network operation.
COM20020-5 with a 40 MHz crystal the bit combinations follow:
A logic "1" on this bit puts the device into Backplane Mode signalling
which is used for Open Drain and Differential Driver interfaces.
These bits determine which register at address 07 may be accessed.
SUBAD1
The combinations are as follows:
0
0
1
1
ET2
0
0
1
1
27
SUBAD0Register
A software reset does not reset the microcontroller
0Tentative ID
1Node ID
0Setup
1Next ID
ET1
0
1
0
1
DESCRIPTION
All nodes should be configured with the
Time ( S)
Response
596.8
298.4
37.35
74.7
IdleTime
( S)
656
328
82
41
Time (mS)
Reconfig
For the
840
840
840
420