EVB-20022 SMSC Corporation, EVB-20022 Datasheet - Page 7

• Manufacturer Part Number: EVB-20022
• Description: Industrial ARCNET AT Adapter Card
• Manufacturer: SMSC Corporation

Direct Coupled RS-485
The direct-coupled RS-485 interface uses RJ-11 connectors with Phase A on pin 3 and Phase B and pin 2. Short
stubs or drops of less than 1 foot can be tolerated but not recommended. The direct-couple RS-485 interface is not
compatible with either the isolated RS-485 or the standard ARCNET twisted pair interfaces. Data rates from 156
Kbps to 10 Mbps are allowed, and the 75ALS176BD (U12) transceiver is used.
To setup the board for direct-coupled interface, with the use of SMSC DEMOAT software, perform the following
steps:
Note:
Note:
Isolated RS-485
The isolated RS-485 interface uses transformer coupling to electrically isolate the data lines and make the
connections insensitive to polarity. Isolation is provided up to 2KV. The isolated RS-485 interface uses RJ-11
connectors with Phase A on pin 3 and Phase B and pin 2. The isolated RS-485 interface is not compatible with direct-
coupled or standard ARCNET interfaces. Data rates from 156 Kbps to 10 Mbps are allowed and the 74ALS1178N
(U13) transformer is used.
To setup the board for isolated RS-485 interface, with the use of SMSC demoat software, and perform the following
steps:
SMSC UG - EVB-20022
1.
2.
3.
4.
5.
Make sure JP8, JP10, JP11, and JP12 are unconnected.
If socketed COM20022 (SKT1) is being utilized, U8 (alternate COM20022 device) must not be mounted on
evaluation board.
1.
2.
3.
4.
5.
Install both jumpers horizontally at JP6 (RJ11 filter)
Install both jumpers horizontally at JP9 (Differential paired data)
Set jumper blocks JP13 and JP5 both to B (Transmit data and receive data)
Set I/O board address as specified in I/O address selection in User Guide (e.g. 02E0)
Set Node ID as specified in Node ID selection in User Guide
Install both jumpers horizontally at JP6 (RJ11 filter)
Install both jumpers horizontally at JP10 (Differential paired data)
Set jumper blocks JP13 and JP5 to C (Transmit data and receive data)
Set I/O board address as specified in I/O address selection in User Guide (e.g. 02E0)
Set Node ID as specified in Node ID selection in User Guide
S3
For proper direct-coupled operation, installed jumpers denoted in black.
SKT1
S2
7
6
DRQ
JP3
5
3
1
0
7
DACK
6
JP2
5
JP4
U8
3
1
1
0
15
12
JP1
IRQ
11
10
Figure 3
9
Page 7
7
5
4
1
U15
3
JP13
A
B
C
D
1
JP5
1
U12
C
D
A
B
U13
JP7
`
U11
T1
JP12
JP10
JP11
JP6
JP8
JP9
1
1
1
1
1
1
LE
D
J2
S1
J1
CO
AX
Rev. 1/5/00