Digi JACKRABBIT BL1800 - Manual (Page 34)

30 Jackrabbit (BL1800)
The Jackrabbit comes with a 220
Ω termination resistor and 681 Ω bias resistors already
installed, as shown in Figure 12.
Figure 12. RS-485 Termination and Bias Resistors
The load these bias and termination resistors present to the RS-485 transceiver (U6) limits
the number of Jackrabbits in a multidrop network to one master and nine slaves, unless the
bias and termination resistors are removed. When using more than 10 Jackrabbits in a
multidrop network, leave the 681
Ω bias resistors in place on the master Jackrabbit, and
leave the 220
Ω termination resistors in place on the Jackrabbit at each end of the network.
3.5.3 Programming Port
The Jackrabbit has a 10-pin program header labeled J3. The programming port uses the
Rabbit 2000’s Serial Port A for communication. Dynamic C uses the programming port to
download and debug programs.
The programming port is also used for the following operations.
• Cold-boot the Rabbit 2000 after a reset.
• Remotely download and debug a program over an Ethernet connection using the
RabbitLink EG2110.
• Fast copy designated portions of flash memory from one Rabbit-based board (the
master) to another (the slave) using the Rabbit Cloning Board.
Alternate Uses of the Serial Programming Port
All three clocked Serial Port A signals are available as
• a synchronous serial port
• an asynchronous serial port, with the clock line usable as a general CMOS input
The serial programming port may also be used as a serial port via the DIAG connector on
the serial programming cable.
U6
R18
681 W
R17
220 W
R16
681 W
485+
485–
6
7
R16
termination
bias
bias
R17
R18
U4
VIN
GND
GND
RESET
JACKRABBIT Z-World, Inc.
GND
PA0
PA2
PA4
PA6
GND
PB0
PB2
PB4
PB6
WDO
GND
PE6
PE4
PE2
PE0
HV0
HV2
K
GND
VCC
PA1
PA3
PA5
PA7
GND
PB1
PB3
PB5
PB7
PCLK
PE7
PE5
PE3
PE1
GND
HV1
HV3
+RAW
VCC GND
RXC
TXC
PC1
PC3
PC5
PC7
AGND
DA1
PD1
PD3
PD5
PD7
GND
485+
VCC
SM1
STAT
VBAT
GND VCC
RXB
TXB
PC0
PC2
PC4
PC6
AD0
DA0
PD0
PD2
PD4
PD6
GND
485–
VCC
SM0
IOBEN
GND
/RST
J5
U6
U5
U3
J4
U1
J1
J2
J3
Y3
Rabbit 2000
SRAM
RS-232
RS-485