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 PortThe 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 inputThe 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
R16terminationbiasbiasR17R18U4
VINGNDGND
RESETJACKRABBITZ-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
J5U6U5U3J4U1J1J2J3Y3Rabbit 2000SRAMRS-232RS-485