Table of Contents
Advertisement
The Jackrabbit comes with a 220 Ω termination resistor and 681 Ω bias resistors already
installed, as shown in Figure 10.
R18
bias
681 W
485+
R17
termination
220 W
485–
R16
bias
681 W
Figure 10. 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.
2.5.3 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. The Rabbit 2000 startup-mode pins
(SMODE0, SMODE1) are presented to the programming port so that an externally con-
nected device can force the Jackrabbit to start up in an external bootstrap mode.
The programming port is used to start the Jackrabbit in a mode where the Jackrabbit will
download a program from the port and then execute the program. The programming port
transmits information to and from a PC while a program is being debugged.
The Jackrabbit can be reset from the programming port.
The Rabbit 2000 status pin is also presented to the programming port. The status pin is an
output that can be used to send a general digital signal.
The clock line for serial port A is presented to the programming port, which makes fast
serial communication possible.
22
U1
U6
6
7
J1
J2
J3
J4
GND
VCC
PA0
PA1
PA2
PA3
U5
PA4
PA5
PA6
PA7
U3
GND
GND
PB0
PB1
PB2
PB3
PB4
PB5
Rabbit 2000
PB6
PB7
WDO
PCLK
GND
PE7
PE6
PE5
PE4
PE3
PE2
PE1
PE0
GND
HV0
HV1
HV2
HV3
K
+RAW
GND
VCC
Y3
JACKRABBIT Z-World, Inc.
U4
J5
VCC
GND
RXB
RXC
TXB
TXC
PC0
PC1
PC2
PC3
PC4
PC5
SRAM
PC6
PC7
AD0
AGND
DA0
DA1
PD0
PD1
PD2
PD3
PD4
PD5
PD6
PD7
GND
GND
R16
485–
485+
VCC
VCC
U6
SM0
SM1
IOBEN
STAT
GND
VBAT
RS-485
/RST
GND
R18
RESET
R17
Jackrabbit (BL1800)
Advertisement
Table of Contents
