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The RCM3700 Prototyping Board comes with a 220 termination resistor and two 681
bias resistors installed and enabled with jumpers across pins 1–2 and 5–6 on header JP1,
as shown in Figure B-9.
Factory
Default
C1
R7
1
5
3
C2
IR1
R1
JP1
JP1
R2
R3
R4
6
4
2
R5
C3
R6
J5
485+
JP1
U3
6
6
5
R16
C22
R21
C26
7
2
1
C23
R23
C24
C25
U7
U8
R24
C27
485–
R25
C28
R26
R27
R28
R30
R31 R32 R33 R34
R29
JP8
J7
C29
THERMISTOR
CONVERT
J8
Figure B-9. RS-485 Termination and Bias Resistors
For best performance, the termination resistors in a multidrop network should be enabled
only on the end nodes of the network, but not on the intervening nodes. Jumpers on boards
whose termination resistors are not enabled may be stored across pins 1–3 and 4–6 of
header JP1.
RabbitCore RCM3700 User's Manual
RXC TXC RXE
R8
J2
R9
J1
GND
GND
C5
C6
/IOWR
/IORD
GND JP2
PE7
PB5
PB4
PB3
C4
U4
PB2
PA0
U3
PA1
C7
R11
C11
R12
PA3
R13
PA5
PA6
R15
PA7
PB0
TCM_SMT_SOCKET
PB7
/RES
+3.3 V
PF0
+5V
PF1
PF4
PF5
PF6
R7
PF7
PC1/PG2
bias
681 W
PC3/
PC0_TXD
PG3
PC2
PE5
TXC
PE4
PE1
R9
L2
C21
termi-
R18 R19
R20
PE0
PG7_RXE
220 W
PG6
nation
PD4
TXE
R22
PD5
VBAT
R8
bias
CX1
CX2
CX3
681 W
RP1
JP4
CX4
UX1
CX5
JP5
JP6
JP7
CX6
CX7
R35 R36
CX8
C35
UX2
CX9
R39 R40
R41 R42
CX11
CX10
DS1
DS2
DS3
R45
R47
R46
R49
RESET
S1
S2
S3
C14
U1
C15
D1
C12
C13
C16
L1
C17
U2
C18
U6
U5
R14
BT1
LCD1JB
LCD1JC
C19
J4
D2
DCIN
LCD1JA
106
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