Hardware User Guide UG-400
Rev. 0 | Page 5 of 20
ISOLATED RS-485 AND RS-422
The isolated RS-485 and RS-422 port is implemented using the
ADM2587E signal and power isolated CAN transceiver. The
ADM2587E connects to UART2 of the ADSP-BF548 and is capable
of functioning at data rates of up to 500 kbit/sec. Figure 4 shows
a circuit diagram of the implementation of the ADM2587E on
the ezLINX hardware.
The RS-485/RS-422 node can be configured using Jumpers JP3,
JP4, JP19, and JP40. To configure the node as a half-duplex RS-485
node, connect JP3, JP4, and JP40. When JP3 and JP4 are fitted,
A to Y are connected and B to Z are connected. When JP3 and
JP4 are removed, the node is configured as a full-duplex RS-422
node. When JP19 is fitted, the A and B pins are terminated with
120 Ω. If termination is not required, remove JP19. When JP40
is connected, a pull-up resistor of 10 kΩ is connected to the
RxD pin (Pin 4) of the ADM2587E. Table 4 shows jumper
configurations for all the interfaces on ezLINX.
The 3.3 V supply is connected to the V
CC
pins (Pin 2 and Pin 8)
to power the isoPower isolated power supply and the iCoupler
signal isolation of the ADM2587E. This generates an isolated
3.3 V on the V
ISOOUT
pin (Pin 12) of the ADM2587E, which is
connected to the V
ISOIN
pin (Pin 19).
A 6-pin screw terminal connector, J7, is used for easy access to the
A (Pin 2 of J7), B (Pin 3 of J7), Z (Pin 4 of J7), Y (Pin 5 of J7), and
RS-485_ISO_GND (Pin 1 and Pin 6 of J7) signals.
The AN-960 Application Note, RS-485/RS-422 Circuit Imple-
mentation Guide, provides more information about implementing
RS-485 and RS-422 circuits.
The ADM2587E contains isoPower technology that uses high
frequency switching elements to transfer power through the
transformer. Special care must be taken during PCB layout to
meet emissions standards. Refer to the AN-0971 Application
Note, Recommendations for Control of Radiated Emissions with
isoPower Devices, for details on board layout considerations.
10649-004
GND
3.3V
RS485_ISO_GND
RS485_ISO_3.3V
GND
3.3V RS485_ISO_3.3V
RS485_ISO_GND
RS485_ISO_GND
3.3V
UART2TX
UART2RX
#RE
DE
C154
10uF
R111
10K
+ +
JP4
JUMPER
C149
0.01uF
+ +
JP19
C152
0.01uF
R66
120R
C150
0.1uF
U16
ADM2587E
GND1
1
VCC
2
GND1
3
RxD
4
RE
5
DE
6
TxD
7
VCC
8
GND1
9
GND1
10
GND2
11
VISOOUT
12
Y
13
GND2
14
Z
15
GND2
16
B
17
A
18
VISOIN
19
GND2
20
C155
0.1uF
J7
SCREW_6
1
2
3
4
5
6
C153
0.1uF
+ +
JP3
JUMPER
C156
0.1uF
C151
10uF
+ +
JP40
Figure 4. ADM2587E Isolated RS-485 and RS-422 Implementation
